Highly corrosion-resistant surface-treated steel sheet and method for producing same

ABSTRACT

The surface-treated steel sheet has a zinc-based plated steel sheet, a surface-treatment coating being formed on the surface of the zinc-based steel sheet by applying and drying a surface treatment coating composition thereon, and a top coating being formed by applying and drying a coating composition for top coating on the surface-treatment coating. The surface treatment coating composition contains a water-epoxy resin dispersion, a silane coupling agent, and phosphoric acid and/or a hexafluorometal acid. The coating composition for top coating contains a high molecular weight epoxy group-containing resin having number average molecular weights ranging from 6000 to 20000.

This application is the United States national phase application ofInternational Application PCT/JP2004/008650 filed Jun. 14, 2004.

TECHNICAL FIELD

The present invention relates to a surface-treated steel sheet withexcellent corrosion resistance and a method for manufacturing thereof.Specifically the present invention relates to an environmentallycompatible surface-treated steel sheet as a surface-treated steel sheetwith excellent corrosion resistance best suitable for outer panels andinner panels of automobile, free from chromium in the manufacturingprocess of the surface-treated steel sheet and within thesurface-treatment coating, and a method for manufacturing thereof.

BACKGROUND ART

Steel sheets such as zinc-based plated steel sheets or aluminum-basedplated steel sheets which are further treated by chromating thereon in atreatment solution containing main ingredients of chromic acid,bichromic acid, or salt thereof have widely been used for the steelsheets for household electric appliances, the steel sheets forbuildings, and the steel sheets for automobiles aiming to improve thecorrosion resistance (resistance to white rust and resistance to redrust). The chromating is an economical treatment method to provideexcellent corrosion resistance and to be conducted relatively easily.

Although chromating uses hexavalent chromium which is a regulatedsubstance for pollution prevention, the hexavalent chromium is treatedin a closed system in the treatment process, thereby being completelyreduced and recovered, and is not emitted to natural environment.Furthermore, the sealing action of organic coating allows very littlethe chromium to elute from the chromate coating so that environment andhuman body are substantially not contaminated by the hexavalentchromium. From the viewpoint of recent global environmental concern,however, the movement of independently decreasing the use of heavymetals including hexavalent chromium has been enhanced. In addition, toprevent the environmental contamination of discarded shredder-dust ofindustrially wasted products, there has been begun a movement toeliminate or to minimize the heavy metals in the products as far aspossible.

Under the situation, there are introduced many treatment technologies toprevent the generation of white rust on zinc-based plated steel sheetwithout applying chromating, or what is called the “chromium-freetechnology”. An example of the chromium-free technology is a methodusing a solution of an inorganic compound, an organic compound, anorganic polymer material, or a combination thereof, adopting immersion,application, electrolytic treatment, and the like to form a thin film onthe zinc-based plated steel sheet.

Typical related technologies are the following.

(1) A method of forming coating by immersing the steel sheet in atreatment solution containing a polyphenol carboxylic acid such astannic acid and a silane coupling agent, or by applying the treatmentsolution onto the steel sheet, (for example, Patent Document 1 andPatent Document 2).

(2) A method of forming coating using a treatment solution containing anorganic resin blended with a polyphenol carboxylic acid such as tannicacid or a phosphoric acid compound, (for example, Patent Documents 3through 6).

(3) A method of applying a coating prepared by blending an organic resinand a silane coupling agent, (for example, Patent Documents 7 through13).

-   Patent Document 1: Japanese Patent Laid-Open No. 7-216268-   Patent Document 2: Japanese Patent No. 2968959-   Patent Document 3: Japanese Patent Laid-Open No. 8-325760-   Patent Document 4: Japanese Patent Laid-Open No. 2000-34578-   Patent Document 5: Japanese Patent Laid-Open No. 2000-199076-   Patent Document 6: Japanese Patent Laid-Open No. 2000-248380-   Patent Document 7: Japanese Patent Laid-Open No. 11-106945-   Patent Document 8: Japanese Patent Laid-Open No. 2000-319787-   Patent Document 9: Japanese Patent Laid-Open No. 2000-248384-   Patent Document 10: Japanese Patent Laid-Open No. 2000-178761-   Patent Document 11: Japanese Patent Laid-Open No. 2000-199076-   Patent Document 12: Japanese Patent Laid-Open No. 2000-281946-   Patent Document 13: Japanese Patent Laid-Open No. 2000-14443

As for the above method (1), there is a method of treatment in anaqueous solution of a polyphenol carboxylic acid, a silane couplingagent, and further a metal ion. An example of the treatment method isthe one described in Patent Document 1. Since, however, the treatmentmethod has a drawback of failing to attain sufficient corrosionresistance, though favorable adhesion of coating is available.

As for the above method (2), Patent Document 3, for example, discloses amethod of treatment using a treatment solution containing a polyphenolcarboxylic acid, an organic resin, and a metal ion. In addition, PatentDocument 4 discloses a method of treatment conducted by immersing thesteel sheet in a treatment solution containing an organic resin and aphosphoric acid compound, or by applying the treatment solution onto thesteel sheet, followed by drying the applied solution. The protectivecoating formed by these treatment solutions cannot attain strongcorrosion resistance which is attained by the chromating, though theprotective coating contributes to the improvement in corrosionresistance to some degree.

As for the above method (3), Patent Documents 8 and 9 disclose a steelsheet having a coating which contains an organic resin, a silanecoupling agent, and further a thiocarbonyl compound, a phosphoric acidcompound, and a vanadium compound. Since, however, the organic resin ispolyurethane or acrylic-olefin resin, the corrosion resistance is notsatisfactory. Patent Document 11 discloses a steel sheet having acoating of acid-modified epoxy resin. Patent Document 10 discloses asteel sheet having a coating prepared by blending a resin which containscopolymerization ingredients of monomer containing hydroxyl group,carboxyl group, glycidyl group, and phosphoric acid group, with a silanecoupling agent and a phosphoric acid compound. Both of these coatings donot give sufficient corrosion resistance. Patent Document 7 discloses asteel sheet having a coating containing a polyvinylphenol derivative, asilane coupling agent, and an etchant such as phosphoric acid. Thecoating also cannot give sufficient corrosion resistance. PatentDocument 12 discloses a steel sheet having a coating containing anorganic resin and an etchant, and Patent Document 13 discloses a steelsheet having a coating containing an organic resin and a silane couplingagent. Both of these Patent Documents do not give detail description,and their coatings have insufficient corrosion resistance.

DISCLOSURE OF THE INVENTION

An object of the-present invention is to provide a surface-treated steelsheet which does not contain chromium in the coating thereof and whichgives excellent corrosion resistance, and a method for manufacturingthereof.

To attain the above object, the present invention provides asurface-treated steel sheet with excellent corrosion resistance thatcontains: a zinc-based plated steel sheet or an aluminum-based platedsteel sheet; a surface-treatment coating having coating thicknessesranging from 0.01 to 1 μm, and being formed by applying and drying asurface treatment coating composition which contains ingredients (a)through (c) described below on a surface of the plated steel sheet; anda top coating having coating thicknesses ranging from 0.3 to 2 μm, andbeing formed by applying and drying a coating composition for topcoating on the surface-treatment coating.

The ingredients (a) through (c) in the surface treatment coatingcomposition are the following.

(a) A water-epoxy resin dispersion which is prepared by dispersing inwater a resin obtained by a reaction of: an (A)polyalkyleneglycol-modified epoxy resin derived from a reaction ofpolyalkyleneglycol having number average molecular weights ranging from400 to 20000, a bisphenol type epoxy resin, an activehydrogen-containing compound, and a polyisocyanate compound; a (B) epoxygroup-containing resin other than the (A) polyalkyleneglycol-modifiedepoxy resin; and an active hydrogen-containing compound in which a partor entire of the compound is structured by a (C) hydrazine derivativehaving active hydrogen.

(b) A silane coupling agent at amounts ranging from 1 to 300 parts bymass of solid matter therein to 100 parts by mass of the resin solidmatter in the water-epoxy resin dispersion.

(c) Phosphoric acid and/or a hexafluorometal acid at amounts rangingfrom 0.1 to 80 parts by mass of solid matter therein to 100 parts bymass of the resin solid matter in the water-epoxy resin dispersion.

The coating composition for top coating contains an (E) high molecularweight epoxy group-containing resin having number average molecularweights ranging from 6000 to 20000.

The present invention further provides a surface-treated steel sheetwith excellent corrosion resistance that contains: a zinc-based platedsteel sheet or an aluminum-based plated steel sheet; a surface-treatmentcoating having coating thicknesses ranging from 0.01 to 1 μm, and beingformed by applying and drying a surface treatment coating compositionwhich contains ingredients (α) through (δ) described below on a surfaceof the plated steel sheet; and a top coating having coating thicknessesranging from 0.3 to 2 μm, and being formed by applying and drying acoating composition for top coating on the surface-treatment coating.

The ingredients (α) through (δ) in the surface treatment coatingcomposition are the following.

(α) A water-epoxy resin dispersion which is prepared by dispersing inwater a (Z) modified epoxy resin obtained by a reaction of a (W) epoxygroup-containing resin, an (X) primary amine compound and/or secondaryamine compound, and an active hydrogen-containing compound in which apart or entire of the compound is structured by a (Y) hydrazinederivative having active hydrogen.

(β) A water dispersed polyurethane resine at amounts of mass ratio ofthe resin solid matter in the water-epoxy resin dispersion to the resinsolid matter in the water dispersed polyurethane resine, [water-epoxyresin dispersion]/[water dispersed polyurethane resine], ranging from95/5 to 5/95.

(γ) A silane coupling agent at amounts ranging from 1 to 300 parts bymass of solid matter therein to 100 parts by mass of the resin solidmatter in the water-epoxy resin dispersion.

(δ) Phosphoric acid and/or a hexafluorometal acid at amounts rangingfrom 0.1 to 80 parts by mass of solid matter therein to 100 parts bymass of the resin solid matter in the water-epoxy resin dispersion.

The coating composition for top coating contains an (E) high molecularweight epoxy group-containing resin having number average molecularweights ranging from 6000 to 20000.

The present invention further provides a method for manufacturingsurface-treated steel sheet with excellent corrosion resistance, whichmethod has the steps of: applying a surface treatment coatingcomposition which contains ingredients (a) through (c) described belowonto a surface of a zinc-based plated steel sheet or an aluminum-basedplated steel sheet, and then drying-the applied surface treatmentcoating composition at ultimate sheet temperatures ranging from 30° C.to 150° C., thus forming a surface-treatment coating having coatingthicknesses ranging from 0.01 to 1 μm; and forming a top coating havingcoating thicknesses ranging from 0.3 to 2 μm on the surface-treatmentcoating by applying a coating composition for top coating, and then bydrying the applied coating composition for top coating at ultimate sheettemperatures ranging from 30° C. to 150° C.

The ingredients (a) through (c) in the surface treatment coatingcomposition are the following.

(a) A water-epoxy resin dispersion which is prepared by dispersing inwater a resin obtained by a reaction of: an (A)polyalkyleneglycol-modified epoxy resin derived from a reaction ofpolyalkyleneglycol having number average molecular weights ranging from400 to 20000, a bisphenol type epoxy resin, an activehydrogen-containing compound, and a polyisocyanate compound; a (B) epoxygroup-containing resin other than the (A) polyalkyleneglycol-modifiedepoxy resin; and an active hydrogen-containing compound in which a partor entire of the compound is structured by a (C) hydrazine derivativehaving active hydrogen.

(b) A silane coupling agent at amounts ranging from 1 to 300 parts bymass of solid matter therein to 100 parts by mass of the resin solidmatter in the water-epoxy resin dispersion.

(c) Phosphoric acid and/or a hexafluorometal acid at amounts rangingfrom 0.1 to 80 parts by mass of solid matter therein to 100 parts bymass of the resin solid matter in the water-epoxy resin dispersion.

The coating composition for top coating contains an (E) high molecularweight epoxy group-containing resin having number average molecularweights ranging from 6000 to 20000.

The present invention further provides a method for manufacturingsurface-treated steel sheet with excellent corrosion resistance, whichmethod has the steps of: applying a surface treatment coatingcomposition which contains ingredients (α) through (δ) described belowonto a surface of a zinc-based plated steel sheet or an aluminum-basedplated steel sheet, and then drying the applied surface treatmentcoating composition at ultimate sheet temperatures ranging from 30° C.to 150° C., thus forming a surface-treatment coating having coatingthicknesses ranging from 0.01 to 1 μm; and forming a top coating havingcoating thicknesses ranging from 0.3 to 2 μm on the surface treatmentcoating by applying a coating composition for top coating, and then bydrying the applied coating composition for top coating at ultimate sheettemperatures ranging from 30° C. to 150° C.

The ingredients (α) through (δ) in the surface treatment coatingcomposition are the following.

(α) A water-epoxy resin dispersion which is prepared by dispersing Inwater a (Z) modified epoxy resin obtained by a reaction of a (W) epoxygroup-containing resin, an (X) primary amine compound and/or secondaryamine compound, and an active hydrogen-containing compound in which apart or entire of the compound is structured by a (Y) hydrazinederivative having active hydrogen.

(β) A water dispersed polyurethane resine at amounts of mass ratio ofthe resin solid matter in the water-epoxy resin dispersion to the resinsolid matter in the water dispersed polyurethane resine, [water-epoxyresin dispersion]/[water dispersed polyurethane resine], ranging from95/5 to 5/95.

(γ) A silane coupling agent at amounts ranging from 1 to 300 parts bymass of solid matter therein to 100 parts by mass of the resin solidmatter in the water-epoxy resin dispersion.

(δ) Phosphoric acid and/or a hexafluorometal acid at amounts rangingfrom 0.1 to 80 parts by mass of solid matter therein to 100 parts bymass of the resin solid matter in the water-epoxy resin dispersion.

The coating composition for top coating contains an (E) high molecularweight epoxy group-containing resin having number average molecularweights ranging from 6000 to 20000.

EMBODIMENTS OF THE INVENTION

The findings derived by the inventors of the present invention and thecorrosion preventive mechanism which is an aim of the present inventionand is derived based on these findings are described in the following.

Corrosion of a zinc-based plated steel sheet with a surface-treatmentcoating thereon is speculated to proceed in the following steps.

(1) Corrosive substances (oxygen, water, chlorine ion, and the like)penetrate into the surface-treatment coating, and they diffuse to theinterface between plated coating and surface-treatment coating.

(2) At the boundary between the plated coating and the surface-treatmentcoating, following-given oxidation-reduction reaction proceeds todissolve zinc.Cathodic reaction: 2H₂O+O₂+4e⁻→4OH⁻Anodic reaction: 2Zn→2Zn²⁺+4e⁻

To improve the corrosion resistance of zinc-based plated steel sheet,therefore, suppression of the progress of both of the above reactions(1) and (2) is essential. To do this, it is effective to structure acoating configuration that contains both of:

(a) a high grade barrier layer which hinders the diffusion of corrosivesubstances; and

(b) a reaction layer with the plated metal to make the surface layer ofthe plated coating inactive. The barrier layer (a) acts mainly tosuppress the above-cathodic reaction, while the reaction layer (b) actsmainly to suppress the above anodic reaction. It is further effectivethat the coating configuration is the one to perform self-repair actionin case that the reactive layer becomes defective.

An investigation found that the effect of improvement in corrosionresistance is attained by actualizing that type of coating configurationin a single layer coating formed by a single application coating, not intwo-layer coating of the related art separately coating the barrierlayer-forming ingredient and the reaction layer-forming ingredient. Indetail, the effect of improvement in corrosion resistance is attained byseparately forming the (a) barrier layer (an organic resin matrix layerdescribed later) on the coating, and forming the (b) reaction layer (anamorphous compound layer described later) under the coating. Preferably,the effect of improvement in corrosion resistance is attained byprecipitating a substance which induces self-repair action in thecoating, thereby inducing a synergy effect. When that type of singlelayer coating is defined as a pseudo-two layer coating, no distinctiveinterface exists between the barrier layer and the reaction layerconfiguring the pseudo-two layer coating, which interface is observedbetween the two layer coatings formed by the two coatings in the priorart. Furthermore, by adopting a gradient composition of these twolayers, higher grade effect of improvement in corrosion resistance thanthat of the single layer coating in the prior art should be attained.

The above-described pseudo-two layer coating can be prepared by applyinga surface treatment coating composition onto the surface of a zinc-basedplated steel sheet or an aluminum-based plated steel sheet, and thenby-drying the composition, which surface treatment coating compositionis prepared by blending a water-dispersed resin obtained by a reactionof a specific modified epoxy resin, a hydrazine derivative having activehydrogen, or other compound, or a water-dispersed modified epoxy resinobtained by a reaction of an epoxy group-containing resin, a primaryamine compound and/or a secondary amine compound, and a hydrazinederivative having active hydrogen, with a silane coupling agent and aspecific acid ingredient (phosphoric acid, hexafluorometal acid, or thelike).

The silane coupling agent is known to have a function to improve theadhesion between an inorganic compound and an organic compound, thus thesilane coupling can increase the adhesion between the plated metal andthe water-dispersible resin. Regarding the known effect of silanecoupling agent, when the above-described specific surface treatmentcoating composition is used, the acid ingredient in the surfacetreatment coating composition presumably activates the surface of theplated coating by etching, and the silane coupling agent presumablychemically bonds the activated plated coating with the coating-formingresin, thereby attaining the extremely strong adhesion between theplated metal and the coating-forming resin. That is, the combinedaddition of a silane coupling agent and a specific acid ingredient tothe surface treatment coating composition presumably increasesdrastically the adhesion between the plated metal and thecoating-forming resin compared with the case of addition of sole silanecoupling agent, thus the proceed of corrosion of the plated metal iseffectively suppressed to attain especially high corrosion resistance.

Although the detail mechanism of forming the pseudo-two layer coatinghaving above-described configuration is not fully analyzed, the reactionbetween the acid ingredient of the surface treatment coating compositionand the surface of plated coating may contribute to the formation ofcoating. On the other hand, there is a speculation offollowing-describing action accompanied with silane coupling agent Thatis, since the silane coupling agent which is hydrolyzed in an aqueoussolution has silanol group (Si—OH), the hydrogen-bonding type adsorptionaction of the silane coupling agent to the surface of plated metal whichis activated by the acid ingredient is enhanced, thus enriching thesilane coupling agent on the surface of plated metal. By succeedingdrying, a dehydration-condensation reaction occurs to establish strongchemical bond, which chemical bond then forms the (b) reaction layerunder the coating, while the water-dispersible resin which is enrichedat upper part of the coating forms the (a) barrier layer. The reactionlayer is a layer reacted with the plated metal which inactivates thesurface layer of the plated coating, and the barrier layer is a strongbarrier layer which acts as a diffusion hindrance to the corrosivesubstances. Furthermore, there is a possibility of occurrence ofcombined above-actions. During the above-described coating-formingprocess, reaction products (compounds) yielded from the reaction betweenthe plated metal such as dissolved zinc and the acid ingredient arepresumably precipitated in the coating.

Although the detail mechanism of corrosion resistance of the pseudo-twolayer coating is not fully analyzed, speculated individual mechanisms ofcorrosion resistance are the following (1) through (5), and presumablytheir combined actions provide the extremely high corrosion resistance(white rust resistance).

(1) By providing an epoxy group-containing resin with a hydrazinederivative, a dense organic polymer coating is formed as the (a) barrierlayer. The organic polymer coating suppresses the permeation ofcorrosive substances (oxygen, water, chlorine ion, and the like), thuseffectively suppressing the cathodic reaction which is a cause ofcorrosion.

(2) Free hydrazine derivative in the coating entraps the plated metalion eluted by the corrosion reaction, thus forming a stable andinsoluble chelating compound layer.

(3) The (b) reaction layer inactivates the surface layer of the platedcoating, thus effectively suppressing the anodic reaction which is acause of corrosion.

(4) The precipitated compound in the coating dissolves in a corrosiveenvironment to form an acid ingredient (phosphoric acid ion, and thelike). As a result, a self-repair action is attained, in which theacidic ingredient entraps metal ion such as zinc ion eluted from theplated coating, (forming an insoluble compound by bonding with the metalion).

(5) The silane coupling agent strongly bonds with the metal surfacewhich is activated by the acid ingredient, thus suppressing thedissolution of plated metal, and also bonds with the coating-formingresin, thereby forming a dense coating having strong adhesion.

Furthermore, by adding a water dispersed polyurethane resine to thesurface treatment coating composition to let the urethane resin exist inthe coating, workability is improved, crack generation in the coatingunder press-working is suppressed, and excellent barrier performance iskept even after working.

By further adding a water-soluble phosphate and a non-chromium basedrust inhibitor to the surface treatment coating composition, superiorcorrosion resistance is attained. For a water-soluble phosphate, similarwith the above-case, the slightly-soluble coating presumably gives thebarrier performance to the corrosive substances, and the phosphoric acidingredient entraps the eluted plated metal ion, thus forming aninsoluble compound with the plated metal ion. In addition, thenon-chromium based rust inhibitor forms a protective coating at theorigin of the corrosion so that the excellent corrosion-preventiveperformance is attained. In actual, those combined effects giveextremely high corrosion preventive performance.

The corrosion-preventive mechanism of the surface-treatment coatingobtained from a specific treatment composition is described above.According to the investigations of the inventors of the presentinvention, however, the sole single layer of that type ofsurface-treatment coating or the sole two-layer coating configuration ofthe surface-treatment coating with a simple organic coating thereongives serious damages at a severe working section under a hold down beador the like found in a press-mold for automobile, and the corrosionresistance is significantly poor. Furthermore, it was found thatalkali-degreasing given to remove oil after working further damages thedamaged portions on the coating, which further deteriorates thecorrosion resistance. To this point, the inventors of the presentinvention conducted further investigations about the coatingconfiguration that highly satisfies the corrosion resistance at workingsection under that severe working and succeeding alkali degreasing, andfound that the high corrosion prevention effect is attained even at thesections subjected to above-described severe working andalkali-degreasing by forming a coating which contains a high molecularweight epoxy group-containing resin having number average molecularweights ranging from 6000 to 20000, or preferably by forming a coatingwhich contains the resin as the main ingredient resin, as the secondarycoating on the above-described surface-treatment coating. That is, thepresent invention attains especially high corrosion resistance atworking sections by the combined actions of the combination ofabove-described specific surface-treatment coating (base coating) with aspecific high molecular weight resin coating.

The present invention was perfected based on the above-describedfindings, and the characteristics of the present invention are thefollowing.

[1] A surface-treated steel sheet with excellent corrosion resistancecontains: a zinc-based plated steel sheet or an aluminum-based platedsteel sheet; a surface-treatment coating having coating thicknessesranging from 0.01 to 1.0 μm, and being formed by applying and drying asurface treatment coating composition which contains ingredients (a)through (c) described below on a surface of the plated steel sheet; anda top coating having coating thicknesses ranging from 0.3 to 2.0 μm, andbeing formed by applying and drying a coating composition for topcoating, containing an (E) high molecular weight epoxy group-containingresin having number average molecular weights ranging from 6000 to 20000on the surface-treatment coating:

(a) a water-epoxy resin dispersion which is prepared by dispersing inwater a resin obtained by a reaction of: an (A)polyalkyleneglycol-modified epoxy resin derived from a reaction ofpolyalkyleneglycol having number average molecular weights ranging from400 to 20000, a bisphenol type epoxy resin, an activehydrogen-containing compound, and a polyisocyanate compound; a (B) epoxygroup-containing resin other than the (A) polyalkyleneglycol-modifiedepoxy resin; and an active hydrogen-containing compound in which a partor entire of the compound is structured by a (C) hydrazine derivativehaving active hydrogen;

(b) a silane coupling agent at amounts ranging from 1 to 300 parts bymass of solid matter therein to 100 parts by mass of the resin solidmatter in the water-epoxy resin dispersion; and

(c) phosphoric acid and/or a hexafluorometal acid at amounts rangingfrom 0.1 to 80 parts by mass of solid matter therein to 100 parts bymass of the resin solid matter in the water-epoxy resin dispersion.

[2] The surface-treated steel sheet with excellent corrosion resistanceaccording to [1], wherein the (C) hydrazine derivative containing activehydrogen is one or more compounds selected from the group consisting ofa pyrazole compound and a triazole compound, which compound has a ringstructure of five-membered ring or six-membered ring, and has nitrogenatom in the ring structure.

[3] The surface-treated steel sheet with excellent corrosion resistanceaccording to [1] or [2], wherein the surface treatment coatingcomposition further contains a water-soluble phosphate at amountsranging from 0.1 to 60 parts by mass of solid matter therein to 100parts by mass of the resin solid matter in the water-epoxy resindispersion of the ingredient (a).

[4] The surface-treated steel sheet with excellent corrosion resistanceaccording to any of [1] through [3], wherein the surface treatmentcoating composition further contains a non-chromium based rust inhibitorat amounts ranging from 0.1 to 50 parts by mass of solid matter thereinto 100 parts by mass of the resin solid matter in the water-epoxy resindispersion of the ingredient (a).

[5] A surface-treated steel sheet with excellent corrosion resistancecontains: a zinc-based plated steel sheet or an aluminum-based platedsteel sheet; a surface-treatment coating having coating thicknessesranging from 0.01 to 1.0 μm, and being formed by applying and drying asurface treatment coating composition which contains ingredients (α)through (δ) described below on a surface of the plated steel sheet; anda top coating having coating thicknesses ranging from 0.3 to 2.0 μm, andbeing formed by applying and drying a coating composition for topcoating, containing an (E) high molecular weight epoxy group-containingresin having number average molecular weights ranging from 6000 to 20000on the surface-treatment coating:

(α) a water-epoxy resin dispersion which is prepared by dispersing ineater a (Z) modified epoxy resin obtained by a reaction of a (W) epoxygroup-containing resin, an (X) primary amine compound and/or secondaryamine compound, and an active hydrogen-containing compound in which apart or entire of the compound is structured by a (Y) hydrazinederivative having active hydrogen;

(β) a water dispersed polyurethane resine at amounts of mass ratio ofthe resin solid matter in the water-epoxy resin dispersion to the resinsolid matter in the water dispersed polyurethane resine, [water-epoxyresin dispersion]/[water dispersed polyurethane resine], ranging from95/5 to 5/95;

(γ) a silane coupling agent at amounts ranging from 1 to 300 parts bymass of solid matter therein to 100 parts by mass of the resin solidmatter in the water-epoxy resin dispersion; and

(δ) phosphoric acid and/or a hexafluorometal acid at amounts rangingfrom 01 to 80 parts by mass of solid matter therein to 100 parts by massof the resin solid matter in the water-epoxy resin dispersion.

[6] The surface-treated steel sheet with excellent corrosion resistanceaccording to [5], wherein the (Y) hydrazine derivative containing activehydrogen is one or more compounds selected from the group consisting ofa pyrazole compound and a triazole compound, which compound has a ringstructure of five-membered ring or six-membered ring, and has nitrogenatom in the ring structure.

[7] The surface-treated steel sheet with excellent corrosion resistanceaccording to [5] or [6] wherein the surface treatment coatingcomposition further contains a water-soluble phosphate at amountsranging from 0.1 to 60 parts by mass of solid matter therein to 100parts-by mass of the resin solid matter in the sum of the water-epoxyresin dispersion of the ingredient (α) and the water dispersedpolyurethane resine of the ingredient (β).

[8] The surface-treated steel sheet with excellent corrosion resistanceaccording to any of [5] through [7], wherein the surface treatmentcoating composition further contains a non-chromium based rust inhibitorat amounts ranging from 0.1 to 50 parts by mass of solid matter thereinto 100 parts by mass of the resin solid matter in the sum of thewater-epoxy resin dispersion of the ingredient (α) and the waterdispersed polyurethane resine of the ingredient (β).

[9] The surface-treated steel sheet with excellent corrosion resistanceaccording to any of [1] through [8], wherein the coating composition fortop coating further contains a non-chromium based rust inhibitor atamounts ranging from 0.1 to 50 parts by mass of solid matter therein to100 parts by mass of the resin solid matter in the coating composition.

[10] The surface-treated steel sheet with excellent corrosion resistanceaccording to any of [1] through [9], wherein the surface treatmentcoating composition for forming a surface-treatment coating and/or acoating composition for top coating contains one or more compoundsselected from the group consisting of (e1) through (e7) given below asthe non-chromium based rust inhibitor:

-   -   (e1) silicon oxide    -   (e2) calcium and/or calcium compound    -   (e3) slightly-soluble phosphoric acid compound    -   (e4) molybdic acid compound    -   (e5) vanadium compound    -   (e6) organic compound containing S atom, being one or more        compounds selected from the group consisting of triazole, thiol,        thiaziazole, thiazole, and thiuram    -   (e7) organic compound containing N atom, being one or more        compounds selected from the group consisting of hydrazide        compound, pyrazole compound, triazole compound, tetrazole        compound, thiaziazole compound, and pyridazine compound.

[11] The surface-treated steel sheet with excellent corrosion resistanceaccording to any of [1] through [10], wherein the coating compositionfor top coating further contains a curing agent having a group whichcrosslinks with hydroxyl group, at amounts ranging from 1 to 50 parts bymass of solid matter therein to 100 parts by mass of the solid matter inthe (E) high molecular weight epoxy group-containing resin.

[12] The surface-treated steel sheet with excellent corrosion resistanceaccording to [11], wherein the curing agent having a group crosslinkingwith hydroxyl group is an (F) amino resin which has one or more iminogroups as an average within a single molecule thereof.

[13] The surface-treated steel sheet with excellent corrosion resistanceaccording to [11], wherein the curing agent having a group crosslinkingwith hydroxyl group is a (G) polyisocyanate compound which has four ormore isocyanate groups as an average within a single molecule thereof.

[14] The surface-treated steel sheet with excellent corrosion resistanceaccording to [13], wherein the (G) polyisocyanate compound is the one inwhich at least some of the isocyanate groups in the polyisocyanatecompound are blocked by a blocking agent.

[15] The surface-treated steel sheet with excellent corrosion resistanceaccording to any of [1] through [14], wherein the (E) high molecularweight epoxy group-containing resin in the coating composition for topcoating is a modified epoxy group-containing resin which is modified byan (H) active hydrogen-containing compound in which a part or entire ofthe compound is structured by an (I) hydrazine derivative having activehydrogen.

[16] The surface-treated steel sheet with excellent corrosion resistanceaccording to any of [1] through [15], wherein the coating compositionfor top coating further contains a solid lubricant at amounts rangingfrom 1 to 30 parts by mass of solid matter therein to 100 parts by massof the resin solid matter in the coating composition.

[17] A method for manufacturing surface-treated steel sheet withexcellent corrosion resistance, which method has the steps of: applyinga surface treatment coating composition which contains ingredients (a)through (c) described below on to a surface of a zinc-based plated steelsheet or an aluminum-based plated steel sheet and then drying theapplied surface treatment coating composition at ultimate sheettemperatures ranging from 30° C. to 150° C., thus forming asurface-treatment coating having coating thicknesses ranging from 0.01to 1.0 μm; and forming a top coating having coating thicknesses rangingfrom 0.3 to 2.0 μm on the surface-treatment coating by applying acoating composition for top coating containing an (E) high molecularweight epoxy group-containing resin having number average molecularweights ranging from 6000 to 20000, and then by drying the appliedcoating composition for top coating at ultimate sheet temperaturesranging from 30° C. to 150° C.:

(a) a water-epoxy resin dispersion which is prepared by dispersing inwater a resin obtained by a reaction of: an (A)polyalkyleneglycol-modified epoxy resin derived from a reaction ofpolyalkyleneglycol having number average molecular weights ranging from400 to 20000, a bisphenol type epoxy resin, an activehydrogen-containing compound, and a polyisocyanate compound; a (B) epoxygroup-containing resin other than the (A) polyalkyleneglycol-modifiedepoxy resin; and an active hydrogen-containing compound in which a partor entire of the compound is structured by a (C) hydrazine derivativehaving active hydrogen;

(b) a silane coupling agent at amounts ranging from 1 to 300 parts bymass of solid matter therein to 100 parts by mass of the resin solidmatter in the water-epoxy resin dispersion; and

(c) phosphoric acid and/or a hexafluorometal acid at amounts rangingfrom 0. 1 to 80 parts by mass of solid matter thereof to 100 parts bymass of the resin solid matter in the water-epoxy resin dispersion.

[18] A method for manufacturing surface-treated steel sheet withexcellent corrosion resistance, which method has the steps of: applyinga surface treatment coating composition which contains ingredients (α)through (δ) described below onto a surface of a zinc-based plated steelsheet or an aluminum-based plated steel sheet, and then drying theapplied surface treatment coating composition at ultimate sheettemperatures ranging from 30° C. to 150° C., thus forming asurface-treatment coating having coating thicknesses ranging from 0.01to 1.0 μm; and forming a top coating having coating thicknesses rangingfrom 0.3 to 2.0 μm on the surface treatment coating by applying acoating composition for top coating containing an (E) high molecularweight epoxy group-containing resin having number average molecularweights ranging from 6000 to 20000, and then by drying the appliedcoating composition for top coating at ultimate sheet temperaturesranging from 30° C. to 150° C.:

(α) a water-epoxy resin dispersion which is prepared by dispersing inwater a (Z) modified epoxy resin obtained by a reaction of a (W) epoxygroup-containing resin, an (X) primary amine compound and/or secondaryamine compound, and an active hydrogen-containing compound in which apart or entire of the compound is structured by a (Y) hydrazinederivative having active hydrogen;

(β) a water dispersed polyurethane resine at amounts of mass ratio ofthe resin solid matter in the water-epoxy resin dispersion to the resinsolid matter in the water dispersed polyurethane resine, [water-epoxyresin dispersion]/[water dispersed polyurethane resine], ranging from95/5 to 5/95;

(γ) a silane coupling agent at amounts ranging from 1 to 300 parts bymass of solid matter therein to 100 parts by mass of the resin solidmatter in the water-epoxy resin dispersion; and

(δ) phosphoric acid and/or a hexafluorometal acid at amounts rangingfrom 0.1 to 80 parts by mass of solid matter therein to 100 parts bymass of the resin solid matter in the water-epoxy resin dispersion.

The surface-treated steel sheet according to the present invention hasextremely high corrosion resistance of sheet before and after workingwithout containing chromium in the coating, and has excellentweldability and coatability. Therefore, the surface-treated steel sheetaccording to the present invention is particularly useful forautomobile.

The following is the detail of the present invention and the reasons tospecify the scope of the present invention.

Applicable zinc-based plated steel sheet as the base of thesurface-treated steel sheet according to the present invention includezinc plated steel sheet, Zn—Ni alloy plated steel sheet, Zn—Fe alloyplated steel sheet (electroplating steel sheet, alloyed hot-dipgalvanized steel sheet), Zn—Cr alloy plated steel sheet, Zn—Mn alloyplated steel sheet, Zn—Co alloy plated steel sheet, Zn—Co—Cr alloyplated steel sheet, Zn—Cr—Ni alloy plated steel sheet, Zn—Cr—Fe alloyplated steel sheet, Zn—Al alloy plated steel sheet (for example, Zn-5%Al alloy plated steel sheet and Zn-55% Al alloy plated steel sheet),Zn—Mg alloy plated steel sheet, Zn—Al—Mg alloy plated steel sheet (forexample, Zn-6% Al-3% Mg alloy plated steel sheet and Zn-11% Al-3% Mgalloy plated steel sheet) and zinc-based composite plated steel sheetprepared by dispersing a metal oxide, a polymer, and the like into theplated coating of these plated steel sheets, (for example, Zn—SiO₂dispersed plated steel sheet).

As of these plated steel sheets, two or more layers of plating with thesame kind or different kinds thereof, or a multilayered plated steelsheet, may be applied.

As the aluminum-based plated steel sheet as the base of thesurface-treated steel sheet according to the present invention, aluminumplated steel sheet, Al—Si alloy plated steel sheet, and the like areapplicable.

The plated steel sheet may be the one prepared by applying a smallcoating weight of Ni or the like onto the surface of the steel sheet, inadvance, followed by coating the above-given plating thereon.

Applicable plating method may be any of adoptable ones includingelectroplating method (electrolysis in an aqueous solution or in anon-aqueous solvent), hot-dip plating method, and chemical vapordeposition method.

To prevent blackening of plating, trace elements of Ni, Co, and Fe maybe precipitated in the plated coating to approximate amounts rangingfrom 1 to 2000 ppm, or a surface-preparation treatment may be given byan alkaline aqueous solution or an acidic aqueous solution containingNi, Co, and Fe onto the surface of plated coating, thereby precipitatingthese elements.

The following is the description about the surface-treatment coatingwhich is formed as the primary coating on the surface of the zinc-basedplated steel sheet or the aluminum-based plated steel sheet, and aboutthe surface treatment coating composition for forming the coating.

For the surface-treated steel sheet according to the present invention,the surface-treatment coating as the first configuration formed on thesurface of the zinc-based plated steel sheet or the aluminum-basedplated steel sheet is a surface-treatment coating which is formed byapplying and drying the surface treatment coating composition containingthe following ingredients (a) through (c). The surface-treatment coatingdoes not contain chromium.

(a) A water-epoxy resin dispersion which is prepared by dispersing inwater a resin obtained by a reaction of: an (A)polyalkyleneglycol-modified epoxy resin derived from a reaction ofpolyalkyleneglycol having number average molecular weights ranging from400 to 20000, a bisphenol type epoxy resin, an activehydrogen-containing compound, and a polyisocyanate compound; a (B) epoxygroup-containing resin other than the (A) polyalkyleneglycol-modifiedepoxy resin; and an active hydrogen-containing compound structured by a(C) hydrazine derivative having active hydrogen; and further at need a(D) active hydrogen-containing compound other than the (C) hydrazinederivative.

(b) A silane coupling agent at amounts ranging from 1 to 300 parts bymass of solid matter therein to 100 parts by mass of the resin solidmatter in the water-epoxy resin dispersion.

(c) Phosphoric acid and/or a hexafluorometal acid at amounts rangingfrom 0.1 to 80 parts by mass of solid matter therein to 100 parts bymass of the resin solid matter in the water-epoxy resin dispersion.

The description begins from the water-epoxy resin dispersion as theingredient (a).

The water-epoxy resin dispersion is obtained by dispersing in water aresin which is prepared by a reaction of: an (A) specifiedpolyalkyleneglycol-modified epoxy resin; a (B) epoxy group-containingresin other than the (A) polyalkyleneglycol-modified epoxy resin; and a(C) hydrazine derivative having active hydrogen; and further at need a(D) active hydrogen-containing compound other than the (C) hydrazinederivative.

The (A) polyalkyleneglycol-modified epoxy resin is obtained by areaction of polyalkyleneglycol having number average molecular weightsranging from 400 to 20000, a bisphenol type epoxy resin, an activehydrogen-containing compound, and a polyisocyanate compound.

Applicable polyalkyleneglycol includes polyethyleneglycol,polypropyleneglycol, and polybutyleneglycol. As of these,polyethyleneglycol is particularly preferred. A suitable range of thenumber average molecular weight of the polyalkyleneglycol is from 400 to20000, preferably from 500 to 10000, in view of water-dispersibility andshelf life of the obtained resin.

The bisphenol type epoxy resin is a bisphenol-based compound having atleast one epoxy group in a single molecule thereof, and adiglycidylether of bisphenol obtained by the condensation reaction of abisphenol-based compound with an epihalohydrin (for example,epichlorohydrin) is particularly preferable in view of easily attaininga coating having excellent elasticity and corrosion prevention.

Typical examples of the bisphenol-based compound applicable forpreparing the bisphenol type epoxy resin are,bis(4-hydroxyphenyl)-2,2-propane, bis(4-hydroxyphenyl)-1,1-ethane,bis(4-hydroxyphenyl)-methane, 4,4′-dihydroxydiphenylether,4,4′-dihydroxydiphenylsulfone, bis(4-hydroxyphenyl)-1,1-isobutane, andbis(4-hydroxy-3-t-butylphenyl)-2,2-propane. As of epoxy resins preparedusing those bisphenol-based compounds, bisphenol-A type epoxy resin isparticularly preferable from the point to attain a coating havingexcellent elasticity and corrosion preventive performance.

From the viewpoint of production stability and other characteristicsduring the manufacture of polyalkyleneglycol-modified epoxy resin,generally the bisphenol type epoxy resin preferably has the numberaverage molecular weight in an approximate range from 310 to 10000, andmore preferably from about 320 to about 2000, and has the epoxyequivalent in a range from about 155 to about 5000, more preferably fromabout 160 to about 1000.

The active hydrogen-containing compound is used for blocking theisocyanate group in the (A) polyalkyleneglycol-modified epoxy resin.Typical examples of the active hydrogen-containing compound are:monohydric alcohol such as methanol, ethanol, and diethyleneglycolmonobutylether; monohydric carboxylic acid such as acetic acid andpropyonic acid; and monohydric thiol such as ethylmercaptan. Otherblocking agent (active hydrogen-containing compound) includes: asecondary amine such as diethylamine; a compound prepared by modifying aprimary amino group in an amine compound such as diethylenetriamine andmonoethanolamine, which amine compound contains one secondary aminogroup or hydroxyl group and one or more primary amino groups, intoaldimine, ketimine, oxazoline, or imidazoline by a heating-reaction withketone, aldehyde, or carboxylic acid at temperatures of, for example,100° C. to 230° C.; an oxime such as methylethylketoxime; and a phenolseries such as phenol and nonylphenol. Generally these compoundspreferably have the number average molecular weights ranging from 30 to2000, more preferably from 30 to 200.

The polyisocyanate compound is a compound having two or more isocyanategroups, preferably two or three isocyanate groups, in a single moleculethereof. The polyisocyanate compounds which are generally used formanufacturing polyurethane resin are also applicable. Those kinds ofpolyisocyanate compounds include the ones of aliphatic, alicyclic, andaromatic. Typical examples of these polyisocyanate compounds are:aliphatic polyisocyanate compound such as hexamethylene diisocyanate(HMDI), biuret compound of HMDI, and isocyanulate compound of HMDI;alicyclic polyisocyanate compound such as isophorone diisocyanate (IPDI)and biuret compound of IPDI, isocyanulate compound of IPDI, hydrogenatedxylylene diisocyanate, and hydrogenated 4,4′-diphenymethanediisocyanate; and aromatic polyisocyanate compound such as tolylenediisocyanate and xylylene diisocyanate.

Generally, the blending rate of individual ingredients for manufacturingthe (A) polyalkyleneglycol-modified epoxy resin is preferably in a rangegiven below.

That is, a preferable equivalent ratio of the hydroxyl group ofpolyalkyleneglycol to the isocyanate group of polyisocyanate compound isfrom 1/1.2 to 1/10, more preferably from 1/1.5 to 1/5, and mostpreferably from 1/1.5 to 1/3. A preferable equivalent ratio of thehydroxyl group of active hydrogen-containing compound to the isocyanategroup of polyisocyanate compound is from 1/2 to 1/100, more preferablyfrom 1/3to 1/50, and most preferably from 1/3 to 1/20. A preferableequivalent ratio of the sum of the hydroxyl groups ofpolyalkyleneglycol, bisphenol type epoxy resin, and activehydrogen-containing compound to the isocyanate group of polyisocyanatecompound is 1/1.5 or smaller, more preferably from 1/0.1 to 1/1.5, andmost preferably from 1/0.1 to 1/1.1.

The reaction of the polyalkyleneglycol, the bisphenol type epoxy resin,the active hydrogen-containing compound, and the polyisocyanate compoundmay be carried out by a known method.

By the reaction of above-prepared (A) polyalkyleneglycol-modified epoxyresin, (B) epoxy group-containing resin other than the (A)polyalkyleneglycol-modified epoxy resin, (C) hydrazine derivative havingactive hydrogen, and further at need (D) active hydrogen-containingcompound other than the (C) hydrazine derivative, an epoxy resin whichis readily dispersed in water and which gives favorable adhesion to basematerial is attained.

Examples of the (B) epoxy group-containing resin other than the (A)polyalkyleneglycol-modified epoxy resin are: an aromatic epoxy resinwhich is prepared by introducing glycidyl group through the reaction ofpolyphenol such as bisphenol-A, bisphenol-F, and novolak type phenolwith epihalohydrin such as epichlorohydrin, or by a further reaction ofthat glycidyl group-introduced reaction product with a polyphenol toincrease the molecular weight; aliphatic epoxy resin; and alicyclicepoxy resin. These epoxy resins may be used separately or in combinationof two or more of them. If the coating formability at low temperaturesis required, these epoxy resins preferably have the number averagemolecular weights of 1500 or more.

An example of the (B) epoxy group-containing resin is a resin which isprepared by a reaction of epoxy group or hydroxyl group in the epoxygroup-containing resin with various modification agents. Examples of the(B) epoxy group-containing resin are: an epoxy-ester resin prepared by areaction with dry oil fatty acid; an epoxy-acrylate resin prepared bymodification using a polymerizable unsaturated monomer ingredientcontaining acrylic acid, methacrylic acid, and the like; and anurethane-modified epoxy resin prepared by a reaction with an isocyanatecompound.

Further example of the (B) epoxy group-containing resin is anacrylic-based copolymer resin, prepared by copolymerizing with an epoxygroup-containing monomer. The acrylic-based copolymer is synthesizedfrom an unsaturated monomer having epoxy group with a polymerizableunsaturated monomer ingredient which essentially contains an acrylicacid ester or a methacrylic acid ester, by solution polymerization,emulsion polymerization, suspension polymerization, and the like.Examples of the polymerizable unsaturated monomer ingredient are: C1-C4alkyl ester of acrylic acid or methacrylic acid, such asmethyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, n-,iso-, or ter-butyl(meth)acrylate, hexyl(meth)acrylate,2-ethylhexyl(meth)acrylate, decyl(meth)acrylate, andlauryl(meth)acrylate; acrylic acid, methacrylic acid, styrene, vinyltoluene, acrylamide, acrylonitrile, N-methylol(meth)acrylamide, andC1-C4 alkyletherified compound of N-methylol(meth)acrylamide; andN,N-diethylaminoethylmethacrylate. The unsaturated monomer having epoxygroup is not specifically limited if only the monomer has an epoxy groupand a polymerizable unsaturated group, such as glycidylmethacrylate,glycidylacrylate, and 3,4-epoxycyclohexyl-1-methy(meth)acrylate.

The acrylic-based copolymer resin may further be modified by polyesterresin, epoxy resin, phenol resin, and the like.

A specifically preferred (B) epoxy group-containing resin is a productof reaction between bisphenol-A and epihalohydrin, which reactionproduct is a resin expressed by the following chemical formula. Thereaction product is particularly preferred owing to the excellentcorrosion resistance.

In the chemical formula, q is integers from 0 to 50, preferably from 1to 40, and more preferably from 2 to 20.

That kind of bisphenol-A type epoxy resin can be manufactured by amethod widely known in the industry concerned.

Examples of the active hydrogen-containing compound which reacts withthe (B) epoxy group-containing resin are the following.

-   -   Hydrazine derivative having active hydrogen    -   Primary or secondary amine compound having active hydrogen    -   Organic acid such as ammonia and carboxylic acid    -   Hydrogen halide such as hydrogen chloride    -   Alcohol, thiol    -   Hydrazine derivative having no active hydrogen or a quaternary        chlorination agent as a mixture with tertiary amine with an        acid.

For preparing the water-epoxy resin dispersion, one or more of abovecompounds may be used. To attain excellent corrosion resistance,however, at least a part (preferably entire) of the activehydrogen-containing compound has to be a hydrazine derivative havingactive hydrogen. That is, as of these compounds, the (C) hydrazinederivative having active hydrogen is the essential ingredient, whileusing the (D) active hydrogen-containing compound other than the (C)hydrazine derivative, at need.

Examples of typical amine compound having active hydrogen, abovedescribed, are the following.

(1) A compound prepared by the heating reaction of a primary amino groupin an amine compound which contains one secondary amino group and one ormore primary amino groups, such as diethylene triamine,hydroxyethylaminoethylamine, ethylaminoethylamine, andmethylaminopropylamine, with ketone, aldehyde, or carboxylic acid, at,for example, approximate temperatures ranging from 100° C. to 230° C.,thus modifying into aldimine, ketimine, oxazoline, or imidazoline.

(2) A secondary monoamine such as diethylamine, diethanolamine, di-n- or-iso-propanolamine, N-methylethanolamine, and N-ethylethanolamine.

(3) A secondary amine-containing compound prepared by the addition of amonoalkanol amine such as monoethanolamine to dialkyl(meth)acrylamide byMichael addition reaction.

(4) A compound prepared by modifying a primary amine group ofalkanolamine such as monoethanolamine, neopentanolamine,2-aminopropanol, 3-aminopropanol, and2-hydoxy-2′(aminopropoxy)ethylether into ketimine.

Regarding the quaternary chlorinating agent applicable as a part of theactive hydrogen-containing compound, since the hydrazine derivativehaving no active hydrogen or the tertiary amine has no reactivity withepoxy group, the respective mixtures with an acid are prepared to makethem reactive with epoxy group. The quaternary chlorinating agent reactswith epoxy group in the presence of, at need, water, thereby forming aquaternary salt with the epoxy group-containing resin. The acid used toobtain the quaternary chlorinating agent may be any of organic acid suchas acetic acid and lactic acid or inorganic acid such as hydrochloricacid. The hydrazine derivative having no active hydrogen, which is usedto obtain the quaternary chlorinating agent, may be3,6-dichloropyridazine. The tertiary amine may be dimethyethanolamine,triethylamine, trimethylamine, triisopropylamine, andmethyldiethanolamine.

As of these active hydrogen-containing compounds, a hydrazine derivativehaving active hydrogen is most useful and gives highest corrosionresistance.

Examples of the hydrazine derivative having active hydrogen are thefollowing.

(a) A hydrazide compound such as carbohydrazide, hydrazide propionate,hydrazide salicylate, dihydrazide adipate, dihydrazide sebacylate,dihydrazide dodecanate, dihydrazide isophthalate, thiocarbohydrazide,4,4′-oxybisbenzenesulfonyl hydrazide, benzophenone hydrazone, andaminopolyacrylamide.

(b) A pyrazole compound such as pyrazole, 3,5-dimethylpyrazole,3-methyl-5-pyrazolone, and 3-amino-5-methylpyrazole.

(c) A triazole compound such as 1,2,4-triazole, 3-amino-1,2,4-triazole,4-amino-1,2,4-triazole, 3-mercapto-1,2,4-triazole,5-amino-3-mercapto-1,2,4-triazole, 2,3-dihydro-3-oxo-1,2,4-triazole,1H-benzotriazole, 1-hydroxybenzotriazole(monohydrate),6-methyl-8-hydroxytriazolopyridazine,6-phenyl-8-hydroxytriazolopyridazine, and5-hydroxy-7-mehyl-1,3,8-triazaindolizine.

(d) A tetrazole compound such as 5-phenyl-1,2,3,4-tetrazole, and5-mercapto-1-phenyl-1,2,3,4-tetrazole.

(e) A thiadiazole compound such as 5-amino-2-mercapto-1,3,4-thiadiazole,and 2,5-dimercapto-1,3,4-thiaziazole.

(f) A pyridazine compound such as hydrazide maleate,6-methyl-3-pyridazone, 4,5-dichloro-3-pyridazone,4,5-dibromo-3-pyridazone, and 6-methyl-4,5-dihydro-3-pyridazone.

As of these compounds, particularly preferred ones are pyrazole compoundand triazole compound having a ring structure of five membered ring orsix membered ring, and having nitrogen atom in the ring structure.

These hydrazine derivatives may be used separately or in combination oftwo or more of them.

The above water-epoxy resin dispersion can be obtained by the reactionof above-described (A) polyalkyleneglycol-modified epoxy resin, the (B)epoxy group-containing resin other than the (A)polyalkyleneglycol-modified epoxy resin, the (C) hydrazine derivativehaving active hydrogen, and further, at need, the (D) activehydrogen-containing compound other than the (C) hydrazine derivative, attemperatures ranging preferably from 10° C. to 300° C., more preferablyfrom 50° C. to 150° C., for about 1 to about 8 hours, followed bydispersing the prepared resin in water.

The above reaction may be conducted adding an organic solvent. Theorganic solvent is not specifically limited. Examples of the solventare: ketone such as acetone, methylethylketone, methylisobutylketone,dibutylketone, and cyclohexanone; alcohol or ether having hydroxylgroup, such as ethanol, butanol, 2-ethylhexylalcohol, benzylalcohol,ethyleneglycol, ethyleneglycol monoisopropylether, ethyleneglycolmonobutylether, ethyleneglycol monohexylether, propyleneglycol,propyleneglycol monomethylether, diethyleneglycol, diethyleneglycolmonoethylether, and diethylene glycol monobutylether; ester such asethylacetate, butylacetate, and ethyleneglycol monobutyletheracetate;aromatic hydrocarbon such as toluene and xylene. One or more of them canbe used. As of these solvents, ketone or ether solvent is particularlypreferred in view of solubility of epoxy resin and ofcoating-formability.

From the point of corrosion resistance and water-dispersibility ofresin, the blending rate of the (A) polyalkyleneglycol-modified epoxyresin, the (B) epoxy group-containing resin other than the (A)polyalkyleneglycol-modified epoxy resin, and the (C) hydrazinederivative having active hydrogen is preferably adjusted so as theequivalent ratio of the epoxy group in the (A)polyalkyleneglycol-modified epoxy resin and the (B) epoxygroup-containing resin to the active hydrogen group in the (C) hydrazinederivative to become in a range from 0.01 to 10, more preferably 0.1 to8, and most preferably from 0.2 to 4.

Some of the (C) hydrazine derivatives having active hydrogen may besubstituted with the (D) active hydrogen-containing compound. From thepoint of corrosion prevention and adhesion, however, the substitutingquantity (or the percentage of the (D) active hydrogen-containingcompound in the active hydrogen-containing compounds including the (C)hydrazine derivative) is preferably 90% by mole or less, more preferably70% by mole or less, and most preferably in a range from 10 to 60% bymole.

To form a dense barrier coating, it is preferable to add a curing agentto the resin composition to heat and cure the coating. Preferred curingmethods to form a coating of resin composition are (1) curing methodutilizing an urethanation reaction between isocyanate and hydroxyl groupin the base resin, and (2) curing method utilizing an etherificationreaction between hydroxyl group in the base resin and alkyl-etherifiedamino resin which is prepared by a reaction between C1-C5 monohydricalcohol and a part or entire of a methylol compound obtained by areaction between formaldehyde and one or more of melamine, urea, andbenzoguanamine. As of these methods, it is particularly preferred toadopt the urethanation reaction between the isocyanate and the hydroxylgroup in the base resin as the main reaction.

The polyisocyanate compound as the curing agent applicable to the (1)curing method is a compound which is prepared by a partial reaction ofaliphatic, alicyclic (including polycyclic) or aromatic isocyanatecompound having at least two isocyanate groups in a single moleculethereof, or a compound of them, with a polyhydric alcohol. Examples ofthat type of polyisocyanate compound are the following.

(A) m- or p-phenylenediisocyanate, 2,4- or 2,6-tolylenediisocyanate, o-or p-xylylenediisocyanate, hexamethylenediisocyanate, dimer aciddiisocyanate, and isophoronediisocyanate.

(B) A reaction product compound obtained by a reaction of sole compoundof or a mixture of the (A) compounds with a polyhydric alcohol (dihydricalcohol such as ethyleneglycol and propyleneglycol, trihydric alcoholsuch as glycerin and trimethylolpropane, tetrahydric alcohol such aspentaerythritol, and hexahydric alcohol such as sorbitol anddipentaerythritol) and having at least two isocyanate left in a singlemolecule thereof.

These polyisocyanate compounds may be used separately or in combinationof two or more of them.

Examples of applicable protective agent (blocking agent) for thepolyisocyanate compound are the following.

(i) An aliphatic monoalcohol such as methanol, ethanol, propanol,butanol, and octylalcohol.

(ii) A monoether of ethyleneglycol and/or diethyleneglycol, such as amonoether of methyl, ethyl, propyl (n-, iso), and butyl (n-, iso, sec).

(iii) An aromatic alcohol such as phenol and cresol.

(iv) An oxime such as acetoxime and methylethylketone oxime.

The reaction of one or more of these blocking agents with thepolyisocyanate compound provides a polyisocyanate compound which isstably protected at least at normal temperature.

A preferred blending rate of the polyisocyanate compound (a2) in thewater-epoxy resin dispersion (a), (above-described ingredient (a)), is,as the curing agent, in a range of (a)/(a2) from 95/5 to 55/45 (massratio of nonvolatile matter), and more preferably (a)/(a2) from 90/10 to65/35. Since polyisocyanate compound is a hygroscopic material, themixing ratio (a)/(a2) above 55/45 deteriorates the adhesion of thesurface-treatment coating. Furthermore, excess ratio enhances themigration of unreacted polyisocyanate compound into the top coating,which induces curing inhibition and insufficient adhesion of the topcoating. Accordingly, the mixing ratio of polyisocyanate compound (a2),(a)/(a2), is preferably 55/45 or smaller.

By the addition of above-described crosslinking agent (curing agent),the water-dispersible resin is fully crosslinked. For further increasingthe crosslinking performance at low temperatures, however, it ispreferred to use a known curing acceleration catalyst. Examples of thecuring acceleration catalyst are N-ethylmorphorine, dibutyltindilaurate, cobalt naphthenate, tin(II)chloride, zinc naphtenate, andbismuth nitrate.

Aiming at the improvement of physical properties such as adhesion, tosome extent, a known resin such as acrylic, alkyd, and polyester resinscan be used blending with the (B) epoxy group-containing resin.

To disperse in water the reaction product of the (A)polyalkyleneglycol-modified epoxy resin, the (B) epoxy group-containingresin, and the (C) hydrazine derivative having active hydrogen, (andfurther, at need, the (D) active hydrogen-containing compound),following-given methods, for example, can be adopted.

(1) A method of conducting reaction between the epoxy group in the epoxygroup-containing resin, (the resin (A) and the resin (B)), and a dibasicacid, a secondary amine, or the like as the active hydrogen-containingcompound, and by neutralizing the reaction product by a tertiary amine,acetic acid, phosphoric acid, and the like as the neutralizing agent,followed by dispersing the product in water.

(2) A method of dispersing the reaction product in water using amodified epoxy resin as the dispersing agent which is prepared by areaction of epoxy resin and polyalkylene oxide containing terminalhydroxyl group, such as polyethyleneglycol and polypropyleneglycol, withisocyanate.

(3) A method of combining (1) with (2).

The surface treatment coating composition may use a water-dispersibleresin and/or a water-soluble resin, other than the above-specifiedwater-dispersible resins, such as one or more of acrylic resin, urethaneresin, polyester resin, epoxy resin, ethylene resin, alkyd resin, phenolresin, and olefin resin, at an upper limit of approximately 15% by massto the total resin solid matter.

The following is the description about the silane coupling agent as theabove ingredient (b).

Examples of the silane coupling agent are vinyl methoxysilane,vinylethoxysilane, vinyltrichlorosilane, vinyltrimethoxysilane,vinyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,γ-glycidoxypropyltrimethoxysilane,γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane,N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane,N-β(aminoethyl)γ-aminopropyltrimethoxysilane,N-β(aminoethyl)γ-aminopropylmethoxysilane,γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane,γ-methacryloxypropylmethyldimetoxysilane,γ-methacryloxypropyltrimethoxysilane,γ-metharcyloxypropylmethyldiethoxysilane,γ-methacryloxypropyltriethoxysilane,γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane,p-styryltrimethoxysilane, γ-acryloxypropyltrimethoxysilane,N-phenyl-γ-aminopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane,γ-chloropropyltrimethoxysilane, bis(triethoxysilylpropyl)tetrasulfide,γ-isocyanatepropyltriethoxysilane,γ-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, andN-(vinylbenzilamine)-β-aminoethyl-γ-aminopropyltrimethoxysilane. Thesecompounds may be used separately or in combination of two or more ofthem.

According to the present invention, the improvement of white rustresistance owing to the existence of silane coupling agent as well asthe specified acid ingredient in the surface treatment coatingcomposition is attained presumably by the reason described before.

As of these silane coupling agents, the one having amino group as thereactive functional group is particularly preferable from the point ofcontaining a functional group having high reactivity with thewater-dispersible resin of the above ingredient (a). Examples of thattype of silane coupling agent areN-β(aminoethyl)γ-aminopropylmethyldimethoxysilane,N-β(aminoethyl)γ-aminopropyltrimethoxysilane,N-β(aminoethyl)γ-aminopropyltrimethoxysilane,γ-aminopropyltrimethoxysilane, and γ-aminopropyltriethoxysilane.Specifically, there are applicable KBM-903, KBE-903, KBM-603, KBE-602,and KBE-603, (trade names; manufactured by Shin-Etsu Chemical Co., Ltd.)

The blending quantity of silane coupling agent is in a range from 1 to300 parts by mass as solid matter to 100 parts by mass of the resinsolid matter in the water-epoxy resin dispersion as the above ingredient(a), preferably from 5 to 100 parts by mass, and more preferably from 15to 50 parts by mass. If the blending quantity of silane coupling agentis smaller than 1 part by mass, the corrosion resistance isdeteriorated. If the blending quantity of silane coupling agent exceeds300 parts by mass, satisfactory coating cannot be formed, which fails toattain the effect of improving the adhesion and the barrier performanceto the water-dispersible resin, thereby deteriorating the corrosionresistance.

The phosphoric acid and/or the hexafluorometal acid as the aboveingredient (c) has a function to activate the plated metal surface byacting onto the inactive plated metal surface. The phosphoric acid andthe hexafluorometal acid may be used separately or in combination ofthem.

Although the kind of hexafluorometal acid is not specifically limited, apreferable one is a hexafluorometal acid which contains one or moreelements selected from the group consisting of Ti, Si, and Zr, such asfluorotitanic acid, fluorozirconic acid, and hydrofluorosilicic acid,and one or more of them can be-used.

The blending quantity of the phosphoric acid and/or the hexafluorometalacid is in a range from 0.1 to 80 parts by mass as solid matter to 100parts by mass of the resin solid matter in the water-epoxy resindispersion as the above ingredient (a) preferably from 1 to 60 parts bymass, and more preferably from 5 to 50 parts by mass. If the blendingquantity of the phosphoric acid and/or the hexafluorometal acid issmaller than 0.1 parts by mass, the corrosion resistance isdeteriorated, and if the blending quantity thereof exceeds 80 parts bymass, the soluble ingredient in the coating increases to deteriorate thecorrosion resistance, both of which cases are not preferable.

In the surface-treated steel sheet according to the present invention,the surface-treatment coating in the second configuration, formed on thesurface of zinc-based plated steel sheet or aluminum-based plated steelsheet, is a surface-treatment coating which is formed by applying thesurface treatment coating composition containing the followingingredients (α) through (δ), and by drying the coating. Thesurface-treatment coating does not contain chromium.

(α) A water-epoxy resin dispersion which is prepared by dispersing inwater a (Z) modified epoxy resin obtained by a reaction of a (W) epoxygroup-containing resin, an (X) primary amine compound and/or secondaryamine compound, and an active hydrogen-containing compound in which apart or entire of the compound is structured by a (Y) hydrazinederivative having active hydrogen.

(β) A water dispersed polyurethane resine at amounts of mass ratio ofthe resin solid matter in the water-epoxy resin dispersion to the resinsolid matter in the water dispersed polyurethane resine, [water-epoxyresin dispersion]/[water dispersed polyurethane resine], ranging from95/5 to 5/95.

(γ) A silane coupling agent at amounts ranging from 1 to 300 parts bymass of solid matter therein to 100 parts by mass of the resin solidmatter in the water-epoxy resin dispersion.

(δ) Phosphoric acid and/or a hexafluorometal acid at amounts rangingfrom 0.1 to 80 parts by mass of solid matter therein to 100 parts bymass of the resin solid matter in the water-epoxy resin dispersion.

First, the description is given about the water-epoxy resin dispersionas the ingredient (α).

The epoxy group-containing resin as the ingredient (W) is a resincontaining one or more epoxy groups in the molecule thereof. Examples ofthat type of epoxy group-containing resin are epoxy resin, modifiedepoxy resin, acrylic-based copolymer resin prepared by copolymerizingepoxy group-containing monomer with other monomer, polybutadiene resinhaving epoxy group, polyurethane resin having epoxy group, and anadditive or a condensate of these resins. These resins may be usedseparately or in combination of two or more of them.

Examples of these epoxy resins are: an aromatic epoxy resin prepared byintroducing glycidyl group through a reaction of polyphenol such asbisphenol-A, bisphenol-F, and novolak type phenol with epihalohydrinsuch as epichlorohydrin, or by a further reaction of that glycidylgroup-introduced reaction product with a polyphenol to increase themolecular weight; an aliphatic epoxy resin; an aliphatic epoxy resin;and an alicyclic epoxy resin. These epoxy resins may be used separatelyor in combination of two or more of them. If the coating formability atlow temperatures is required, these epoxy resins preferably have thenumber average molecular weights of 1500 or more.

An example of the modified epoxy resin is a resin which is prepared by areaction of epoxy group or hydroxyl group in the above epoxy resin withvarious modification agents. Examples of the modified epoxy resin are:an epoxy-ester resin prepared by a reaction with dry oil fatty acid; anepoxy-acrylate resin prepared by modification using a polymerizableunsaturated monomer ingredient containing acrylic acid, methacrylicacid, or the like; and an urethane-modified epoxy resin prepared by areaction with an isocyanate compound.

An example of the acrylic-based copolymer resin is a resin which issynthesized from an unsaturated monomer having epoxy group with apolymerizable unsaturated monomer ingredient which essentially containsan acrylic acid ester or a methacrylic acid ester, by solutionpolymerization, emulsion polymerization, suspension polymerization, andthe like. Examples of the polymerizable unsaturated monomer ingredientare: C1-C24 alkyl ester of acrylic acid or methacrylic acid, such asmethyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, n-,iso-, or ter-butyl(meth)acrylate, hexyl(meth)acrylate,2-ethylhexyl(meth)acrylate, decyl(meth)acrylate, andlauryl(meth)acrylate; acrylic acid, methacrylic acid, styrene, vinyltoluene, acrylamide, acrylonitrile, N-methylol(meth)acrylamide,N-methylol(meth)acrylamide, C1-C4 alkyletherified compound ofN-methylol(meth)acrylamide, and N,N-diethylaminoethyl methacrylate.

The unsaturated monomer having epoxy group is not specifically limitedif only the monomer has an epoxy group and a polymerizable unsaturatedgroup, such as glycidylmethacrylate, glycidylacrylate, and3,4-epoxycyclohexyl-1-methy(meth)acrylate.

The acrylic-based copolymer resin may further be modified by polyesterresin, epoxy resin, phenol resin, and the like.

A specifically preferred (W) epoxy group-containing resin is abisphenol-A type resin which is a product of reaction betweenbisphenol-A and epihalohydrin. The resin can be obtained by a knownmanufacturing method.

The primary amine compound and/or the secondary amine compound as theingredient (X) is essential to obtain water-dispersibility of the epoxygroup-containing resin.

Examples of the primary amine-compound and/or the secondary aminecompound are: a primary amine compound such as monoethylamine, mono-n-or iso-propylamine, mono n- or iso-butylamine, monoethanolamine,neopentanolamine, 2-aminopropanol, 3-aminopropanol, and2-hydroxy-2′(aminopropoxy) ethylether; and a secondary amine compoundsuch as diethylamine, dibutylamine, methylethylamine, diethanolamine,di-n- or -iso-propanoplaime, N-methylethanolamine, andN-ethylethanolamine. These primary or secondary amine compounds may beused separately or in combination of two or more of them. As of theseprimary or secondary amine compounds, diethanolamine is preferred inview of easiness in reaction, controllability, and water-dispersibility.

The hydrazine derivative having active hydrogen, as the ingredient (Y),is an essential ingredient to provide the coating with excellentcorrosion resistance. Examples of the hydrazine derivative having activehydrogen are the following.

(a) A hydrazide compound such as carbohydrazide, hydrazide propionate,hydrazide salicylate, dihydrazide adipate, dihydrazide sebacylate,dihydrazide dodecanate, dihydrazide isophthalate, thiocarbohydrazide,4,4′-oxybisbenzenesulfonyl hydrazide, benzophenone hydrazone, andaminopolyacrylamide.

(b) A pyrazole compound such as pyrazole, 3,5-dimethylpyrazole,3-methyl-5-pyrazolone, and 3-amino-5-methylpyrazole.

(c) A triazole compound such as 1,2,4-triazole, 3-amino-1,2,4-triazole,4-amino-1,2,4-triazole, 3-mercapto-1,2,4-triazole,5-amino-3-mercapto-1,2,4-triazole, 2,3-dihydro-3-oxo-1,2,4-triazole,1H-benzotriazole, 1-hydroxybenzotriazole(monohydrate),6-methyl-8-hydroxytriazolopyridazine,6-methyl-8-hydroxytriazolopyridazine, and5-hydroxy-7-mehyl-1,3,8-triazaindolizine.

(d) A tetrazole compound such as 5-phenyl-1,2,3,4-tetrazole, and5-mercapto-1-phenyl-1,2,3,4-tetrazole.

(e) A thiadiazole compound such as 5-amino-2-mercapto-1,3,4-thiadiazole,and 2,5-dimercapto-1,3,4-thiaziazole.

(f) A pyridazine compound such as hydrazide maleate,6-methyl-3-pyridazone, 4,5-dichloro-3-pyridazone,4,5-dibromo-3-pyridazone, and 6-methyl-4,5-dihydro-3-pyridazone.

As of these compounds, particularly preferred ones from the point ofcorrosion resistance and other characteristics are pyrazole and triazolecompounds having a ring structure of five membered ring or six memberedring, and having nitrogen atom in the ring structure.

These hydrazine derivatives may be used separately or in combination oftwo or more of them.

Some of the (Y) hydrazine derivative shaving active hydrogen may besubstituted with an active hydrogen-containing compound other than thehydrazine derivative. That is, according to the present invention, anactive hydrogen-containing compound other than the (Y) hydrazinederivative having active hydrogen may be used for some of the activehydrogen-containing compounds.

Examples of the active hydrogen-containing compound other than the (Y)hydrazine derivative are the following.

-   -   Organic acid such as ammonia and carboxylic acid    -   Hydrogen halide such as hydrogen chloride    -   Alcohol, thiol    -   Hydrazine derivative having no active hydrogen or a quaternary        chlorination agent as a mixture of tertiary amine and acid.

Regarding the quaternary chlorinating agent applicable as a part of theactive hydrogen-containing compound, since the hydrazine derivativehaving no active hydrogen or the tertiary amine has no reactivity withepoxy group, the respective mixtures with an acid are prepared to makethem reactive with epoxy group. The quaternary chlorinating agent reactswith epoxy group in the presence of, at need, water, thereby forming aquaternary salt with the epoxy group-containing resin. The acid used toobtain the quaternary chlorinating agent may be any of organic acid suchas acetic acid and lactic acid or inorganic acid such as hydrochloricacid. The hydrazine derivative having no active hydrogen, which is usedto obtain the quaternary chlorinating agent, may be3,6-dichloropyridazine. The tertiary amine may be dimethyethanolamine,triethylamine, trimethylamine, triisopropylamine, andmethyldiethanolamine.

The percentage of the (Y) hydrazine derivative having active hydrogen inthe active hydrogen-containing compound is in a range from 10 to 100% bymole, preferably from 30 to 100% by mole, and most preferably from 40 to100% by mole. If the percentage of the (Y) hydrazine derivative havingactive hydrogen is less than 10% by mole, satisfactory rust-preventivefunction cannot be given to the surface-treatment coating, and theobtained rust-prevention effect is very little different from that inthe case of simple mixing of a coating-forming resin with a hydrazinederivative.

To obtain the (Z) modified epoxy resin, generally it is preferable toconduct reaction between the (W) epoxy group-containing resin, the (X)primary amine compound and/or secondary amine compound, and an activehydrogen-containing compound in which a part or entire of the compoundis structured by a (Y) hydrazine derivative having active hydrogen attemperatures ranging from 10° C. to 300° C., preferably from 50° C. to150° C. for about 1 to about 8 hours.

The reaction may be done adding an organic solvent, and the kind of thesolvent is not specifically limited. Examples of the solvent are: ketonesuch as acetone, methylethylketone, methylisobutylketone, dibutylketone,and cyclohexanone; alcohol or ether having hydroxyl group, such asethanol, butanol, 2-ethylhexylalcohol, benzylalcohol, ethyleneglycol,ethyleneglycol monoisopropylether, ethyleneglycol monobutylether,ethyleneglycol monohexylether, propyleneglycol, propyleneglycolmonomethylether, diethyleneglycol, diethyleneglycol monoethylether, anddiethyleneglycol monobutylether; ester such as ethylacetate,butylacetate, and ethyleneglycol monobutyletheracetate; and aromatichydrocarbon such as toluene and xylene. One or more of them can be used.As of these solvents, ketone or ether solvent is particularly preferredin view of solubility of epoxy resin and of coating-formability.

The blending percentage of the (W) epoxy group-containing resin and the(X) primary amine compound and/or secondary amine compound is preferablyin a range from 20 to 80% by mole of the (X) amine compound to the epoxygroup in the (X) epoxy group-containing resin, more preferably from 30to 70% by mole, and most preferably from 40 to 60% by mole. From thepoint of corrosion resistance and water-dispersibility, it is preferableto let the (Y) hydrazine derivative having active hydrogen react by anequivalent quantity to the residual epoxy groups after the reaction.Accordingly, the (Y) hydrazine having active hydrogen is preferablyadded by percentages ranging from 80 to 20% by mole to the epoxy groupsin the (W) epoxy group-containing resin, more preferably from 70 to 30%by mole, and most preferably from 60 to 40% by mole.

An available method to prepare a resin dispersion by dispersing the (Z)modified epoxy resin in water is the neutralization using acetic acid,formic acid, phosphoric acid, and the like, which are the knownneutralizing agents to amino group in the (Z) modified epoxy resin,followed by dispersing in water. Although the neutralization equivalentis not specifically limited, it is preferred to select the range thereoffrom 0.2 to 0.8 equivalent to amino groups, more preferably from 0.3 to0.7 equivalent, and most preferably from 0.4 to 0.6 equivalent, from thepoint of property of dispersion and of water resistance.

The water-epoxy resin dispersion according to the present invention canform a coating having good adhesion with metal and the like by applyingand drying the water-epoxy resin dispersion. To form a denser barriercoating, however, it is preferable to add a (J) curing agent to thewater-epoxy resin dispersion to heat and cure the organic coating. The(J) curing agent may be a polyisocyanate compound and an amino resincompound.

The polyisocyanate compound is a compound having at least two isocyanategroups in a single molecule thereof. Examples of the polyisocyanatecompound are: an aliphatic isocyanate compound; an alicyclic isocyanatecompound (including polycycdic one); an aromatic isocyanate compound;and a compound which is prepared by partial reaction of these isocyanatecompounds by a polyhydric alcohol. Some of or all of the isocyanategroups in these polyisocyanate compounds may be blocked by a blockingagent.

Examples of the polyisocyanate compound are the following.

(a) m- or p-phenylenediisocyanate, 2,4- or 2,6-tolylenediisocyanate, o-or p-xylylenediisocyanate, hexamethylenediisocyanate, dimer aciddiisocyanate, and isophoronediisocyanate.

(b) A reaction product compound obtained by a reaction of sole (a)compound or of a mixture of (a) compounds with a polyhydric alcohol(dihydric alcohol such as ethyleneglycol and propyleneglycol, trihydricalcohol such as glycerin and trimethylpropane, tetrahydric alcohol suchas pentaerythritol, and hexahydric alcohol such as sorbitol anddipentaerythritol), and having at least two isocyanates left in a singlemolecule thereof.

These polyisocyanate compounds may be used separately or in combinationof two or more of them.

Examples of blocking agent are: (1) aliphatic monoalcohol such asmethanol, ethanol, propanol, butanol, and octylalcohol; (2) monoether ofethyleneglycol and/or diethyleneglycol, such as monoether of methyl,ethyl, propyl (n-, iso), butyl (n-, iso, sec); (3) aromatic alcohol suchas phenol and cresol; and (4) oxime such as a cetoxime andmethylethylketone oxime. The reaction of one or more of these blockingagents with the polyisocyanate compound provides a polyisocyanatecompound which is stably protected at least at normal temperature.

The amino resin includes a methylolated amino resin which is prepared bya reaction between an aldehyde and an amino ingredient such as melamine,urea, benzoguanamine, acetoguanamine, steroguanamine, spiroguanamine,and dicyandiamide. The aldehyde includes formaldehyde, paraformaldehyde,acetoaldehyde, and benzaldehyde. A compound prepared by etherifying themethylolated amino resin by an appropriate alcohol can also be used.Examples of the alcohol applicable to the etherification aremethylalcohol, ethylalcohol, n-propylalcohol, i-propylalcohol,n-butylalcohol, i-butylalcohol, 2-ethylbutanol, and 2-ethylhexanol.

For the amino resin, a methylolated melamine resin prepared byalkyletherifying at least some of the methylol groups is particularlypreferable.

The blending ratio of the (Z) modified epoxy resin to the (J) curingagent, (Z)/(J), is preferably in a range from 95/5 to 55/45 by mass ofsolid matter, and more preferably from 90/10 to 65/35, in view ofadhesion of coating to the base material and of adequacy of top coating.

For further increasing the crosslinking performance at low temperatures,however, it is preferred to use a known curing acceleration catalyst.Examples of the curing acceleration catalyst for the case thatpolyisocyanate compound is used as the curing agent areN-ethylmorphorine, dibutyltin dilaurate, cobalt naphthenate,tin(II)chloride, zinc naphtenate, and bismuth nitrate. Applicable curingacceleration catalyst in the case of using an amino resin as the curingagent includes phosphoric acid, sulfonic acid compound, or anamine-neutralized sulfonic acid compound. Typical examples of thesulfonic acid compound are p-toluenesulfonate, dodecylbenzenesulfonate,dinonylnaphthalene sulfonate, and dinonylnaphthalenedisulfonate. Theamine in the amine-neutralized sulfonic acid compound may be any ofprimary amine, secondary amine, and tertiary amine.

The following is the description about the water dispersed polyurethaneresine as the ingredient (β).

The water dispersed polyurethane resine is an urethane emulsion using aproduct of a reaction between a polyisocyanate compound and apolyhydroxy compound such as polyetherdiol and polyesterdiol.

The urethane emulsion can be readily obtained by, for example, areaction between a polyisocyanate compound and a polyhydroxy compound inthe presence or in the absence of a hydrophilic organic solvent whichhas no active hydrogen reactive with isocyanate group in the moleculethereof under a condition of excess isocyanate groups of thepolyisocyanate compound to the hydroxyl groups in the polyhydroxycompound. At need, the reaction product (polymer), an amine, and waterare mixed together to let the mixture conduct amine-extension reaction,and then a nonionic or ionic emulsifying agent is added to the reactionproduct, and further water is added to the mixture to make the productemulsify and disperse, and then, at need, the organic solvent isdistilled out.

By using a polyol which has nonionic, anionic, or cationic hydrophilicgroup in the urethane resin skeleton, the urethane emulsion is preparedwithout using emulsifying agent.

Examples of the polyisocyanate compound are: organic diisocyanateincluding aliphatic diisocyanate such as hexamethylene diisocyanate andtrimethylhexamethylene diisocyanate, alicyclic diisocyanate such ashydrogenated xylylene diisocyanate and isophorone diisocyanate, andaromatic diisocyanate such as tolylene diisocyanate and4,4′-diphenylmethane diisocyanate; and a cyclization polymer of aboveorganic diisocyanates; and further isocyanulate and biuret compound ofabove organic diisocyanates.

From the point of mixing stability with water-epoxy resin dispersion, aparticularly preferable water dispersed polyurethane resine is nonionicor cationic polyurethane emulsion.

The blending ratio of the (α) water-epoxy resin dispersion to the (β)water dispersed polyurethane resine in the surface treatment coatingcomposition, [water-epoxy resin dispersion]/[water dispersedpolyurethane resine], is preferably in a range from 95/5 to 5/95 as massratio of the resin solid matter in the water-epoxy resin dispersion tothe solid matter in the water-epoxy resin dispersion, more preferablyfrom 75/25 to 25/75. By adding the water dispersed polyurethane resine,the corrosion resistance after forming is effectively improved comparedwith the case of without addition of the water dispersed polyurethaneresine. A presumable reason of the improvement is that the addition ofan appropriate quantity of water dispersed polyurethane resine improvesthe coating-formability of the surface treatment coating composition,which allows preventing the penetration of corrosive substances, whichprevents the outflow of rust inhibitor ingredient from the coating, andwhich suppresses the crack generation in the resin coating after theworking, thereby improving the corrosion resistance. If the blendingratio of the (α) water-epoxy resin dispersion to the (β) water dispersedpolyurethane resine becomes smaller than the above lower limit, thecoating-formability by the urethane resin becomes insufficient, and thesuppression effect to the corrosive substances becomes unsatisfactory,thus likely deteriorating the white rust resistance. On the other hand,if the blending ratio of the (α) water-epoxy resin dispersion to the (β)water dispersed polyurethane resine becomes larger than the above upperlimit, the percentage of the hydrazine derivative having active hydrogenin the surface treatment coating composition decreases, which alsolikely decreases the white rust resistance.

Other than the above specific water-dispersible resins, the surfacetreatment coating composition may contain one or more of otherwater-dispersible resin and/or water-soluble resin, for example, acrylicresin, polyester resin, epoxy resin, ethylene resin, alkyd resin, phenolresin, and olefin resin, at amounts of about 25% by mass as solid matterto the total resin solid matter.

The following is the description about the silane coupling agent as theingredient (γ).

Examples of the silane coupling agent are vinylmethoxysilane,vinylethoxysilane, vinyltrichlorosilane, vinyltrimethoxysilane,vinyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,γ-glycidoxypropyltrimethoxysilane,γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane,N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane,N-β(aminoethyl)γ-aminopropyltrimethoxysilane,N-β(aminoethyl)γ-aminopropyltrimethoxysilane,γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane,γ-methacryloxypropylmethyldimetoxysilane,γ-metacryloxypropyltrimethoxysilane,γ-metharcyloxypropylmethyldiethoxysilane,γ-methacryloxypropyltriethoxysilane,γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane,p-styryltrimethoxysilane, γ-acryloxypropyltrimethoxysilane,N-phenyl-γ-aminopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane,γ-chloropropyltrimethoxysilane, bis(triethoxysilylpropyl)tetrasulfide,γ-isocyanatepropyltriethoxysilane,γ-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, andN-(vinylbenzilamine)-β-aminoethyl-γ-aminopropyltrimethoxysilane. Thesecompounds may be used separately or in combination of two or more ofthem.

According to the present invention, the improvement of white rustresistance owing to the existence of silane coupling agent as well asthe specified acid ingredient in the surface treatment coatingcomposition is attained presumably by the reason described before.

As of these silane coupling agents, the one having amino group as thereactive functional group is particularly preferable from the point thatthe water-dispersible resin of the above (α) ingredient contains ahighly reactive functional group. Examples of that type of silanecoupling agent are N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane,N-⊖(aminoethyl)γ-aminopropyltrimethoxysilane,N-β(aminoethyl)γ-aminopropyltrimethoxysilane,γ-aminopropyltrimethoxysilane, and γ-aminopropyltriethoxysilane.Specifically, there are applicable KBM-903, KBE-903, KBM-603, KBE-602,and KBE-603, (trade names; manufactured by Shin-Etsu Chemical Co., Ltd.)

The blending quantity of silane coupling agent is preferably in a rangefrom 1 to 300 parts by mass as solid matter to 100 parts by mass of theresin solid matter in the water-epoxy resin dispersion as the aboveingredient (α), more preferably from 5 to 100 parts by mass, and mostpreferably from 15 to 50 parts by mass. If the blending quantity ofsilane coupling agent is smaller than 1 part by mass, the corrosionresistance is deteriorated. If the blending quantity of silane couplingagent exceeds 300 parts by mass, satisfactory coating cannot be formed,which fails to attain the effect of improving the adhesion and thebarrier performance to the water-dispersible resin, therebydeteriorating the corrosion resistance.

The phosphoric acid and/or the hexafluorometal acid as the aboveingredient (δ) has a function to activate the plated metal surface byacting onto the inactive plated metal surface. The adhesion between thusactivated plated metal surface and the coating-forming resin issignificantly improved owing to the silane coupling agent, therebymarkedly improving the corrosion resistance. The phosphoric acid and thehexafluorometal acid may be used separately or in combination of them.

Although the kind of hexafluorometal acid is not specifically limited, apreferable one is a hexafluorometal acid which contains one or moreelements selected from the group consisting of Ti, Si, and Zr, such asfluorotitanic acid, fluorozirconic acid, and hydrofluorosilicic acid,from the above-described point that the reaction layer of pseudo-twolayer coating is effectively formed. One or more of them can be used.

The blending quantity of the phosphoric acid and/or the hexafluorometalacid is preferably in a range from 0.1 to 80 parts by mass as solidmatter to 100 parts by mass of the resin solid matter in the water-epoxyresin dispersion as the above ingredient (α), more preferably from 1 to60 parts by mass, and most preferably from 5 to 50 parts by mass. If theblending quantity of the phosphoric acid and/or the hexafluorometal acidis smaller than 0.1 parts by mass, the corrosion resistance isdeteriorated, and if the blending quantity thereof exceeds 80 parts bymass, the soluble ingredient in the coating increases to deteriorate thecorrosion resistance, both of which cases are not preferable.

The following is the description of common matter for thesurface-treatment coating in the first and the second configurations.

For improving the corrosion resistance, the surface treatment coatingcomposition may contain, at need, a water-soluble phosphate. Examples ofthe water-soluble phosphate are one or more of metal salt thereof suchas ortho phosphoric acid, diphosphonic acid, polyphosphoric acid, andmethaphosphoric acid. Furthermore, one or more of salt of organicphosphoric acid (for example, phytic acid, phytinate, phosphonic acid,phosphonate, and their metal salt) may be added. As of these,diphosphate is preferred in view of stability of the surface treatmentcoating composition and other characteristics.

There is no specific limitation in the configuration of phosphate in thecoating, and the phosphate may be in crystal or amorphous state.Furthermore, there is no specific limitation in the ionicity andsolubility of phosphate in the coating. A presumable reason ofimprovement of corrosion resistance by the addition of a water-solublephosphate is that the water-soluble phosphate forms a dense andslightly-soluble compound during the coating-forming stage.

As described before, the silane coupling agent establishes a chemicalbond with both the activated plated metal and the coating-forming resin,thereby providing excellent adhesion between the plated metal and thecoating-forming resin, and excellent corrosion resistance. Since,however, the surface of plated metal unavoidably has inactive site, theinactive site is difficult to generate the chemical bond, and fails tofully perform the rust-preventive effect. To that plated coatingportion, the water-soluble phosphate forms a dense and slightly-solublecompound during the coating-forming stage. That is, along with thedissolution of the plated coating by the action of the phosphoric acidion in the water-soluble phosphate, the pH increases at the interfacebetween the plated coating and the surface treatment coatingcomposition. As a result, a precipitate coating of the water-solublephosphate is formed, which coating contributes to the improvement ofcorrosion resistance.

For attaining especially excellent corrosion resistance, Al, Mn, Ni, andMg are particularly preferred as the cation species of the water-solublephosphate. It is preferable to use a water-soluble phosphate thatcontains one or more of these cations. Examples of that type ofwater-soluble phosphate are aluminum diphosphate, manganese diphosphate,nickel diphosphate, and magnesium diphosphate. As of these, aluminumdiphosphate is most preferable. The mole ratio of the cationicingredient to the P₂O₅ ingredient, [cation]/[P₂O₅], is preferably in arange from 0.4 to 1.0. If the mole ratio [cation]/[P₂O₅] is smaller than0.4, the soluble phosphate deteriorates the insoluble property of thecoating, which deteriorates the corrosion resistance, and if the moleratio [cation]/[P₂O₅] exceeds 1.0, the stability of treatment-solutionis significantly deteriorated, both of which cases are not preferable.

For the surface-treatment coating in the first configuration, theblending quantity of the water-soluble phosphate is preferably in arange from 0.1 to 60 parts by mass as solid matter to 100 parts by massof the resin solid matter in the water-epoxy resin dispersion as theingredient (a), more preferably from 0.5 to 40 parts by mass, and mostpreferably from 1 to 30 parts by mass. For the surface-treatment coatingin the second configuration, a preferable blending quantity is in arange from 0.1 to 60 parts by mass of resin solid matter to 100 parts bymass of the resin solid matter in the sum of the water-epoxy resindispersion of the ingredient (α) and the water dispersed polyurethaneresine of the ingredient (β), more preferably from 0.5 to 40 parts bymass, and most preferably from 1 to 30 parts by mass. If the blendingquantity of the water-soluble phosphate is smaller than 0.1 parts bymass, the effect of improvement in the corrosion resistance isinsufficient, and if the blending quantity thereof exceeds 60 parts bymass, the soluble ingredient in the coating increases, both of whichcases are not preferable.

The surface treatment coating composition may contain a non-chromiumbased rust inhibitor, at need, aiming to improve the corrosionresistance. By blending a non-chromium based rust inhibitor in thesurface treatment coating composition, especially excellent corrosionpreventive performance (self-repair performance) is attained.

The non-chromium based rust inhibitor of one or more of thefollowing-given compounds (e1) through (e7) is particularly preferable.

-   -   (e1) silicon oxide    -   (e2) calcium and/or calcium compound    -   (e3) slightly-soluble phosphoric acid compound    -   (e4) molybdic acid compound    -   (e5) vanadium compound    -   (e6) organic compound containing S atom, being one or more        compounds selected from the group consisting of triazole, thiol,        thiaziazole, thiazole, and thiuram    -   (e7) organic compound containing N atom, being one or more        compounds selected from the group consisting of hydrazide        compound, pyrazole compound, triazole compound, tetrazole        compound, thiaziazole compound, and pyridazine compound.

The detail of these non-chromium based rust inhibitors (e1) through(e7), and their corrosion preventive mechanism are the following.

For the ingredient (e1), colloidal silica and dry silica, which are thefine particle silica, may be used. In view of corrosion resistance,however, it is preferable to use calcium ion exchanged silica which isprepared by bonding calcium onto the surface of the fine particlesilica.

Examples of the colloidal silica are SNOWTEX O, 20, 30, 40, C, and S,(trade names; manufactured by Nissan Chemical Industries, Co., Ltd.)Examples of the fumed silica are AEROSIL R971, R812, R811, R974, R202,R805, 130, 200, 300, and 300CR, (trade names; manufactured by NipponAerosil Co., Ltd.) Examples of calcium ion exchanged silica are SHIELDEXC303, SHIELEX AC3, SHIELDEX AC5, (trade names; manufactured by W. R.Grace & Co.), and SHIELDEX, SHELDEX SY710, (trade names; manufactured byFuji Silysia Chemical, Ltd.) These kinds of silica contribute to theformation of a dense and stable zinc corrosion product in a corrosiveenvironment. By the creation of the corrosion product densely on thesurface of the plating, the corrosion progress is suppressed.

The ingredients (e2) and (e3) provide especially excellent corrosionpreventive performance (self-repair performance) owing to theirprecipitation action.

The calcium compound as the ingredient (e2) may be any of calcium oxide,calcium hydroxide, and calcium salt, and one or more of them can beused. There is no specific limitation of the calcium salt, and there maybe used a simple salt such as calcium silicate, calcium carbonate, andcalcium phosphate, which contain only calcium as the cation, and adouble salt such as calcium-zinc phosphate and calcium-magnesiumphosphate, which contain calcium ion and cation other than calcium. Theingredient (e2) suppresses the corrosion reaction through thepreferential dissolution of calcium, which is less noble than zinc andaluminum which are the plating metals, under a corrosive environment,which dissolved-calcium then forms a dense and slightly-soluble productwith OH⁻ generated by the cathodic reaction to seal the defectivesection. When the ingredient (e2) is blended with above-describedsilica, calcium ion is adsorbed onto the surface and is coagulated byelectrically neutralizing the surface charge. As a result, a dense andslightly-soluble protective coating is formed, which protective coatingthen seals the origin of corrosion to suppress the corrosion reaction.

The slightly-soluble phosphoric acid compound as the ingredient (e3) mayuse a slightly-soluble phosphate. The slightly-soluble phosphateincludes all kinds of salts such as simple salt and double salt. Themetal cation to structure the slightly-soluble phosphate has no specificlimitation, and any metal cation of slightly-soluble zinc phosphate,magnesium phosphate, calcium phosphate, aluminum phosphate, and the likemaybe applied. In addition, there is no limitation of the skeleton andthe condensation degree of phosphoric acid ion, and there are applicableany of normal salt, dihydrogen salt, monohydrogen salt, and phosphite.Furthermore, normal salt includes all kinds of condensed phosphates suchas polyphosphate, other than orthophosphate. With the use of theslightly-soluble phosphoric acid compound, zinc and aluminum of theplating metal, dissolved by corrosion, and phosphoric acid iondissociated by hydrolysis conduct the complex-forming reaction to form adense and slightly-soluble protective coating, thus sealing the originof corrosion to suppress the corrosion reaction.

As the molybdic acid compound of the ingredient (e4), a molybdate may beused. The molybdate has no limitation of the skeleton and condensationdegree thereof, and there are applicable orthomolybdate, paramolybdate,and methamolybdate. The molybdate includes all kinds of salts such assimple salt and double salt. An example of the double salt is phosphoricacid—molybdic acid salt. The molybdic acid compound generatesself-repair performance by the passivation effect. That is, with thedissolved oxygen, the molybdic acid compound forms a dense oxide on thecoating surface in a corrosive environment, thereby sealing the originof corrosion to suppress the corrosion reaction.

Applicable vanadium compound of the ingredient (e5) includes pentavalentvanadium compound and tetravalent vanadium compound. From the point ofcorrosion resistance, tetravalent vanadium is particularly preferred.

Examples of the organic compound of the ingredient (e6) are thefollowing. As triazole, there are applicable 1,2,4-triazole,3-amino-1,2,4-triazole, 3-mercapto-1,2,4-triazole,5-amino-3-mercapto-1,2,4-triazole, 1H-benzotriazole, and the like. Asthiol, there are applicable 1,3,5-triazine-2,4,6-trithiol,2-mercaptobenzimidazole, and the like. As thiaziazole, there areapplicable 5-amino-2-mercapto-1,3,4-thiadiazole,2,5-dimercapto-1,3,4-thiaziazole, and the like. As thiazole, there areaapplicable 2-N,N-diethylthiobenzothiazole, 2-mercaptobenzothiazole, andthe like. As thiuram, there are applicable tetrathiuramdisulfide, andthe like. These organic compounds generate self-repair performance bythe adsorption effect. That is, zinc and aluminum eluted by corrosionare adsorbed to the polar group containing sulfur in these organiccompounds, thus forming an inactive coating to seal the origin ofcorrosion, thereby suppressing the corrosion reaction.

Examples of the organic compound of the ingredient (e7) are thefollowing. As the hydrazide compound, there are applicablecarbohydrazide, hydrazidepropionate, hydrazidesalicylate,dihydrazideadipate, dihydrazidesebacylate, dihydrazidedodecanate,dihydrazideisophthalate, thiocarbohydrazide,4,4′-oxybisbenzenesulfonylhydrazide, benzophenonehydrazone,aminopolyacrylamide, and the like. As the pyrazole compound, there areapplicable pyrazole, 3,5-dimethylpyrazole, 3-methyl-5-pyrazolone,3-amino-5-methylpyrazole, and the like. As the triazole compound, therearea applicable 1,2,4-triazole, 3-amino-1,2,4-triazole,4-amino-1,2,4-triazole, 3-mercapto-1,2,4-triazole,5-amino-3-mercapto-1,2,4-triazole, 2,3-dihydro-3-oxo-1,2,4-triazole,1H-benzotriazole, 1-hydroxybenzotriazole(monohydrate),6-phenyl-8-hydroxytriazolopyridazine,6-methyl-8-hydroxytriazolopyridazine,5-hydroxy-7-methyl-1,3,8-triazaindolizine, and the like. As thetetrazole compound, there are applicable 5-phenyl-1,2,3,4-tetrazole,5-mercapto-1-phenyl-1,2,3,4-tetrazole, and the like. As the thiaziazolecompound, there are applicable 5-amino-2-mercapto-1,3,4-thiaziazole,2,5-dimercapto-1,3,4-thiadiazole, and the like. As the pyridazinecompound, there are applicable hydrazidemaleate, 6-methyl-3-pyridazone,4,5-dichloro-3-pyridazone, 4,5-dibromo-3-pyridazone,5-methyl-4,5-dihydro-3-pyridazone, and the like. As of these, pyrazolecompound and triazole compound which have ring structure withfive-membered ring or six-membered ring and which have nitrogen atom inthe ring structure are particularly preferable.

For the case of surface-treatment coating in the first configuration,the blending quantity of the non-chromium based rust inhibitor ispreferably in a range from 0.1 to 50 parts by mass as solid matter to100 parts by mass of the resin solid matter in the water-epoxy resindispersion as the ingredient (a), more preferably from 0.5 to 30 partsby mass. For the case of surface-treatment coating in the secondconfiguration, a preferable blending quantity is in a range from 0.1 to50 parts by mass of solid matter to 100 parts by mass of the resin solidmatter in the sum of the water-epoxy resin dispersion of the ingredient(α) and the water dispersed polyurethane resine of the ingredient (β),more preferably from 0.5 to 30 parts by mass. If the blending quantityof the non-chromium based rust inhibitor is smaller than 0.1 parts bymass, the effect of improvement in the corrosion resistance afteralkaline degreasing is insufficient, and if the blending quantitythereof exceeds 50 parts by mass, the coatability and the workabilitydeteriorate, and the corrosion resistance also deteriorates, both ofwhich cases are not preferable.

Two or more of the above (e1) through (e7) rust inhibitors may be addedin combination thereof. In that case, since the respective inherentcorrosion preventive actions are combined, stronger corrosion resistanceis attained. In particular, when the ingredient (e1) adopts a calciumion exchanged silica, and one or mote of (e3) through (e7) ingredients,particularly all of the (e3) through (e7) ingredients, are added incombination, specifically excellent corrosion resistance is attained.

The surface-treatment coating (and the surface treatment coatingcomposition) may further contain one or more of other oxide fineparticles (aluminum oxide, zirconium oxide, titanium oxide, ceriumoxide, antimony oxide, and the like), phosphomolybdic acid salt(aluminum phosphomolybdate, and the like), and organic inhibitor(hydrazine and its derivative, thiol compound, thiocarbamate, and thelike), as the rust inhibitor.

Furthermore, at need, the surface-treatment coating (and the surfacetreatment coating composition) may contain one or more of organiccoloring pigment (condensed polycyclic organic pigment,phthalocyanine-based organic pigment, and the like), coloring dye(water-soluble azo-based metal dye, and the like) inorganic pigment(titanium oxide, and the like), conductive pigment (metal powder ofzinc, aluminum, nickel, and the like, iron phosphide, antimony-doped tinoxide, and the like, coupling agent (titanium coupling agent, and thelike), and melamine-cyanuric acid additive, and the like), as theadditive.

The surface-treatment coating formed by the surface treatment coatingcomposition containing the above ingredients has dry coating thicknessesranging from 0.01 to 1.0 μm, preferably from 0.1 to 0.8 μm. If the drycoating thickness is smaller than 0.01 μm, the corrosion resistance isinsufficient, and if the dry coating thickness is larger than 1.0 μm,the conductivity and the workability deteriorate.

The following is the description about the top coating (organic coating)formed on the surface-treatment coating (the surface-treatment coatingsof the first configuration and the second configuration) as thesecondary coating.

The top coating is a coating having thicknesses ranging from 0.3 to 2.0μm, formed by applying a coating composition for top-coating, whichcomposition contains an (E) high molecular weight epoxy group-containingresin having number average molecular weights ranging from 6000 to20000, or which preferably contains the (E) resin as the main ingredientresin, and then by drying the applied resin. The top coating also doesnot contain chromium. By forming that specific high molecular weightresin coating on the specific surface-treatment coating (base coating)especially strong corrosion resistance at the working section isattained owing to the combined action of both coatings.

According to the present invention, the (E) epoxy group-containing resinis adopted as the top coating because the (E) epoxy group-containingresin is superior in reactivity, readiness of reaction, corrosionprevention, and other characteristics to other resins. Examples of the(E) epoxy group-containing resin are epoxy resin, modified epoxy resin,acrylic-based copolymer resin prepared by copolymerizing with epoxygroup-containing monomer, polybutadiene resin having epoxy group,polyurethane resin having epoxy group, and an additive or a condensateof these resins. These epoxy group-containing resins may be usedseparately or in combination of two or more of them.

As of these (E) epoxy group-containing resins, epoxy resin and modifiedepoxy resin are particularly preferable in view of adhesion with platingsurface and of corrosion resistance. Among them, thermosetting epoxyresin and modified epoxy resin having excellent insulation performanceto the corrosive substances such as oxygen are most suitable, and areparticularly advantageous to make the coating weight of the coating lowlevel for attaining high grade spot-weldability.

As the (E) epoxy group-containing resin, high molecular weight epoxygroup-containing resins having number average molecular weights rangingfrom 6000 to 20000, preferably from 700 to 12000, are adopted. Amongthem, bisphenol type epoxy resins are preferred. The generally-usedbisphenol type epoxy resins have 5500 or smaller number averagemolecular weight. If, however, the number average molecular weightthereof is smaller than 6000, the workability of the obtained coating isnot sufficient, and the coating induces serious damages during severeworking under a hold down bead in a press-mold for automobile, and thecorrosion resistance at the working section deteriorates. If the numberaverage molecular weight thereof exceeds 20000, the manufacture of epoxyresin becomes extremely difficult, and gelling or other phenomena hinderobtaining stable quality of the product.

Examples of the bisphenol type epoxy resin are any of a resin which isprepared by condensing epichlorohydrin with bisphenol in the presenceof, at need, a catalyst such as alkali catalyst to high molecularweight, and a resin which is prepared by condensing epichlorohydrin withbisphenol in the presence of, at need, a catalyst such as alkalicatalyst to a low molecular weight epoxy resin, which low molecularweight epoxy resin is further subjected to polyaddition reaction withbisphenol. To attain stably the high molecular weight epoxy resin,however, the latter method is preferable.

Examples of the bisphenol are bis (4-hydroxyphenyl)methane [bisphenolF], 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane[bisphenol A], 2,2-bis(4-hydroxyphenyl)butane [bisphenol B],bis(4-hydroxyphenyl)-1,1-isobutane,bis(4-hydroxy-tert-butyl-phenyl)-2,2-propane, p-(4-hydroxyphenyl)phenol,oxybis(4-hydroxyphenyl), sulfonylbis(4-hydroxyphenyl),4,4′-dihydroxybenzophenone, and bis(2-hydroxynaphthyl)methane. As ofthese, bis(4-hydroxydiphenyl)methane [bisphenol F] and2,2-bis(4-hydroxyphenyl)propane [bisphenol A] are preferred. The abovebisphenols may be used separately or in combination of two or more ofthem.

The modified epoxy resins include acrylic-modified epoxy resin,polyester-modified epoxy resin, and urethane-modified epoxy resin.Furthermore, there area applicable a polyalkyleneglycol-modified epoxyresin which is prepared by the reaction ofpolyalkyleneglycol,polyisocyanate, and epoxy resin, and a modified epoxyresin (hydrazine derivative-modified epoxy resin) which is prepared bythe reaction of epoxy resin with an active hydrogen-containing compoundin which a part or entire of the compound is structured by a hydrazinederivative having active hydrogen. As of these, hydrazinederivative-modified epoxy resin is particularly preferable in view ofimproving the corrosion resistance.

The modified epoxy resin may be the one prepared by the reaction ofepoxy group or hydroxyl group in the above epoxy resin with variousmodifying agents. Examples of the modified epoxy resin are an epoxyester resin prepared by a reaction with dry fatty acid, an epoxyacrylate resin prepared by modifying by a polymerizable unsaturatedmonomer ingredient containing acrylic acid or methacrylic acid, and anurethane-modified epoxy resin prepared by a reaction with isocyanatecompound.

Examples of the acrylic-based copolymer resin prepared by thecopolymerization with the above epoxy group-containing monomer are theresins synthesized from an unsaturated monomer having epoxy group and apolymerizable unsaturated monomer ingredient which essentially containsan acrylic acid ester or a methacrylic acid ester, by solutionpolymerization, emulsion polymerization, suspension polymerization, andthe like.

Examples of the polymerizable unsaturated monomer ingredient are: C1-C24alkyl ester of acrylic acid or methacrylic acid, such asmethyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, n-,iso-, or ter-butyl(meth)acrylate, hexyl(meth)acrylate,2-ethylhexyl(meth)acrylate, decyl(meth)acrylate, andlauryl(meth)acrylate; acrylic acid, methacrylic acid, styrene, vinyltoluene, acrylamide, acrylonitrile, N-methylol(meth)acrylamide, andC1-C4 alkyletherified compound of N-methylol(meth)acrylamide; andN,N-diethylaminoethyl methacrylate.

The unsaturated monomer having epoxy group is not specifically limitedif only the monomer has an epoxy group and a polymerizable unsaturatedgroup, such as glycidylmethacrylate, glycidylacrylate, and3,4-epoxycyclohexylmethyl(meth)acrylate.

The modified epoxy group-containing resin, represented by the abovehydrazine derivative-modified epoxy resin, which is prepared by thereaction of an (H) active hydrogen-containing compound in which a partor entire of the compound is structured by an (I) hydrazine derivativehaving active hydrogen with an (E) high molecular weight epoxygroup-containing resin, provides improved adhesion with base coating andforms a coating having particularly superior corrosion resistance by thereaction between the epoxy group in the(E) high molecular weight epoxygroup-containing resin with the (I) hydrazine derivative having activehydrogen.

Examples of the (H) active hydrogen-containing compound reacting withthe epoxy group of the (E) high molecular weight epoxy group-containingresin are the following, and one or more thereof may be applied. Also inthis case, it is essential that at least a part (preferably entire) ofthe (H) active hydrogen-containing compound is the (I) hydrazinederivative having active hydrogen. That is, the (I) hydrazine derivativehaving active hydrogen is adopted as the essential ingredient, and atneed, the (H) active hydrogen-containing compound other than the (I)hydrazine derivative is adopted.

-   -   Hydrazine derivative having active hydrogen    -   Primary or secondary amine compound having active hydrogen    -   Organic acid such as ammonia and carboxylic acid    -   Hydrogen halide such as hydrogen chloride    -   Alcohol, thiol    -   Hydrazine derivative having no active hydrogen or a quaternary        chlorination agent as a mixture of tertiary amine with an acid.

Examples of the (I) hydrazide derivative having active hydrogen are thefollowing.

(a) A hydrazide compound such as carbohydrazide, hydrazide propionate,hydrazide salicylate, dihydrazide adipate, dihydrazide sebacylate,dihydrazide dodecanate, dihydrazide isophthalate, thiocarbohydrazide,4,4′-oxybisbenzenesulfonyl hydrazide, benzophenone hydrazone, andaminopolyacrylamide.

(b) A pyrazole compound such as pyrazole, 3,5-dimethylpyrazole,3-methyl-5-pyrazolone, and 3-amino-5-methylpyrazole.

(c) A triazole compound such as 1,2,4-triazole, 3-amino-1,2,4-triazole,4-amino-1,2,4-triazole, 3-mercapto-1,2,4-triazole,5-amino-3-mercapto-1,2,4-triazole, 2,3-dihydro-3-oxo-1,2,4-triazole,1H-benzotriazole, 1-hydroxybenzotriazole(monohydrate),6-methyl-8-hydroxytriazolopyridazine,6-phenyl-8-hydroxytriazolopyridazine, and5-hydroxy-7-mehyl-1,3,8-triazaindolizine.

(d) A tetrazole compound such as 5-phenyl-1,2,3,4-tetrazole, and5-mercapto-1-phenyl-1,2,3,4-tetrazole.

(e) A thiadiazole compound such as 5-amino-2-mercapto-1,3,4-thiadiazole,and 2,5-dimercapto-1,3,4-thiaziazole.

(f) A pyridazine compound such as hydrazide maleate,6-methyl-3-pyridazone, 4,5-dichloro-3-pyridazone,4,5-dibromo-3-pyridazone, and 6-methyl-4,5-dihydro-3-pyridazone.

As of these compounds, particularly preferred ones are pyrazole andtriazole compounds having a ring structure of five membered ring or sixmembered ring, and having nitrogen atom in the ring structure.

These hydrazine derivatives may be used separately or in combination oftwo or more of them.

Typical examples of the amine compound having active hydrogen,applicable to a part of the (H) active hydrogen-containing compound arethe following.

(1) A compound prepared by the heating reaction of a primary amino groupin an amine compound which contains one secondary amino group such asdiethylenetriamine, hydroxyethylaminoethylamine, ethylaminoethylamine,and methylaminopropylamine and one or more of primary amino group, withketone, aldehyde, or carboxylic acid at, for example, approximatetemperatures ranging from 100° C. to 230° C., thus modifying toaldimine, ketimine, oxazoline, or imidazoline.

(2) A secondary monoamine such as diethylamine, diethanolamine, di-n- or-iso-propanolamine, N-methylethanolamine, and N-ethylethanolamine.

(3) A secondary amine-containing compound prepared by the addition of amonoalkanol amine such as monoethanolamine to dialkyl(meth)acrylamide byMichael addition reaction.

(4) A compound prepared by modifying a primary amine group ofalkanolamine such as monoethanolamine, neopentanolamine,2-aminopropanol, 3-aminopropanol, and2-hydoxy-2′(aminopropoxy)ethylether into ketimine.

Regarding the quaternary chlorinating agent applicable as a part of the(H) active hydrogen-containing compound, since the hydrazine derivativehaving no active hydrogen or the tertiary amine have no reactivity withepoxy group, the respective mixtures with an acid are prepared to makethem reactive with epoxy group. The quaternary chlorinating agent reactswith epoxy group in the presence of, at need, water, thereby forming aquaternary salt with the epoxy group-containing resin.

The acid used to obtain the quaternary chlorinating agent may be any oforganic acid such as acetic acid and lactic acid and inorganic acid suchas hydrochloric acid. The hydrazine derivative having no activehydrogen, which is used to obtain the quaternary chlorinating agent,maybe 3,6-dichloropyridazine. The tertiary amine may bedime-thylethanolamine, triethylamine, trimethylamine, triisopropylamine,and methyldiethanolamine.

The product of the reaction of the (E) high molecular weight epoxygroup-containing resin and the (H) active hydrogen-containing compoundin which a part or entire of the compound is structured by an (I)hydrazine derivative having active hydrogen is prepared by the reactionof the (E) high molecular weight epoxy group-containing resin and the(H) active hydrogen-containing compound at temperatures ranging from 10°C. to 300° C., preferably from 50° C. to 150° C., for about 1 to about 8hours.

The above reaction may be conducted adding an organic solvent. Theorganic solvent is not specifically limited. Examples of the organicsolvent are: ketone such as acetone, methylethylketone,methylisobutylketone, dibutylketone, and cyclohexanone; alcohol or etherhaving hydroxyl group, such as ethanol, butanol, 2-ethylhexylalcohol,benzylalcohol, ethyleneglycol, ethyleneglycol monoisopropylether,ethyleneglycol monobutylether, ethyleneglycol monohexylether,propyleneglycol, propyleneglycol monomethylether, diethyleneglycol,diethyleneglycol monoethylether, and diethyleneglycol monobutylether;ester such as ethylacetate, butylacetate, and ethyleneglycolmonobutyletheracetate; aromatic hydrocarbon such as toluene and xylene.One or more of them can be used. As of these solvents, ketone or ethersolvent is particularly preferred in view of solubility of epoxy resinand of coating-formability.

The blending quantity of the (E) high molecular weight epoxygroup-containing resin to the (H) active hydrogen-containing compound inwhich a part or entire of the compound is structured byan (I) hydrazinederivative having active hydrogen is preferably in a range from 0.5 to20 parts by mass of solid matter to 100 parts by mass of solid matter inthe (E) high molecular weight epoxy group-containing resin (A), and morepreferably from 1.0 to 10 parts by mass.

The blending ratio of the (H) active hydrogen-containing compound to the(E) high molecular weight epoxy group-containing resin, as the number ofactive hydrogen groups in the (H) active hydrogen-containing compound tothe number of epoxy groups in the (E) high molecular weight epoxygroup-containing resin, or [(the number of active hydrogen groups)/(thenumber of epoxy groups)], is preferably in a range from 0.01 to 10, morepreferably from 0.1 to 8, and most preferably from 0.2 to 4, from thepoint of corrosion resistance.

The percentage of the (I) hydrazine derivative having active hydrogen inthe (H) active hydrogen-containing compound is preferably in a rangefrom 10 to 100% by mole, more preferably from 30 to 100% by mole, andmost preferably from 40 to 100% by mole. If the percentage of the (I)hydrazine derivative having active hydrogen is smaller than 10% by mole,the top coating fails to attain sufficient rust preventive function, andthe obtained rust prevention effect becomes almost similar with that inthe case of simple-mixing of a coating-forming organic resin and ahydrazine derivative.

The coating composition for top coating according to the presentinvention contains the (E) high molecular weight epoxy group-containingresin as an essential ingredient. By adding a curing agent which canreact with the hydroxyl group in the high molecular weight epoxygroup-containing resin, the coating crosslinks during the heating anddrying stage after applying, thus forming a dense coating having moreexcellent workability and giving barrier performance. Preferable curingmethods for forming the resin composition coating include a curingmethod which utilizes urethanation reaction between the (G)polyisocyanate compound and hydroxyl group in the epoxy group-containingresin, and a curing method which utilizes etherification reactionbetween the (F) amino resin and hydroxyl group in the epoxygroup-containing resin.

The (F) amino resin includes a methylolated amino resin which isprepared by a reaction between an amino ingredient such as melamine,urea, benzoguanamine, acetoguanamine, steroguanamine, spiroguanamine,and dicyandiamide, and an aldehyde ingredient such as formaldehyde,paraformaldehyde, acetoaldehyde, and benzaldehyde. A compound preparedby etherifying the methylol group in the methylolated amino resin by alower alcohol of C1 to C6 is also included in the above amino resins.

As for the above amino resins, there are particularly preferable amethyl-etherified melamine resin prepared by etherifying a part or allof methylol groups in the methyloled melamine resin by methyl alcohol, abutyl-etherified melamine resin prepared by butyl-etherifying bybutylether, and a mixed etherified melamine resin of methyl ether andbutyl ether, which is etherified by both methyl alcohol and butylalcohol. As of these, use of a methyl-etherified melamine resincontaining 1 or more imino groups as an average in a single moleculethereof, preferably 1.5 or more thereof, allows increasing the lowtemperature reactivity with the (E) high molecular weight epoxygroup-containing resin, thereby significantly increasing the strength ofthe coating. Commercially available amino resins include Cymel 325,Cymel 327, and Cymel 703, (trade names; manufactured by Mitsui Cytec,Ltd.)

The above amino resins may be used separately or in combination of twoor more of them.

Examples of the (G) polyisocyanate compound are: aliphatic diisocyanatesuch as hexamethylene diisocyanate and trimethylhexamethylenediisocyanate; alicyclic diisocyanate such as hydrogenated xylylenediisocyanate and isophorone diisocyanate; aromatic diisocyanate such astolylenediisocyanate and 4,4′-diphenylmethane diisocyanate; organicpolyisocyanate itself such as a polyisocyanate compound having three ormore isocyanate groups, includingtriphenylmethane-4,4′,4″-triisocyanate, 1,3,5-triisocyanatebenzene,2,4,6-triisocyanatetoluene, and4,4′-dimethyldiphenylmethane-2,2′,5,5′-tetraisocyanate; an additive ofeach of these organic polyisocyanates with polyhydric alcohol, lowmolecular weight polyester resin, water, or the like; cyclized polymerof above organic polyisocyanates; and isocyanate biuret compound.

Among them, polyisocyanate compounds having 4 or more isocyanate groups,preferably 6 to 10 thereof, in a single molecule can form strongercoating even at decreased reaction temperatures owing to the densecrosslink with the (E) high molecular weight epoxy group-containingresin, thus providing particularly good corrosion resistance at workingsection under severe working. Examples of that type of polyisocyanatecompound are: an adduct of4,4′-dimethyldiphenylmethane-2,2′,5,5′-tetraisocyanate; and an adduct ofhexamethylenediisocyanate.

The (G) polyisocyanate compound may be the one in which a part or all ofthe isocyanate groups thereof is blocked by a blocking agent. Examplesof the blocking agent are: phenol series including phenol, cresol, andxylenol; lactam series including ε-caprolactam, δ-valerolactam,γ-butylolactam, and β-propyolactam; alcohol series including methanol,ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutylalcohol, tert-butyl alcohol, ethyleneglycol monoethylether,ethyleneglycol monobutylether, diethyleneglycol monoethylether,propyleneglycolmonomethylether, and benzyl alcohol; oxime seriesincluding formamidoxime, acetoaldoxime, acetoxime, methylethylketoxime,diacetylmonoxime, benzophenoneoxime, and cyclohexaneoxime; and activemethylene series including dimethyl malonate, diethyl malonate, ethylacetoacetate, methyl acetoacetate, and acetyl acetone.

Commercially available polyisocyanate compounds containing 4 or moreisocyanate groups in a single molecule thereof include MF-B80M, MF-B60X,MF-K60X, and ME20-B80S, (trade names; manufactured by Asahi KaseiChemicals Corporation)

From the point of curing performance, preferable content of the curingagent in the coating composition for top coating is in a range from 1 to50 parts by mass of solid matter, more preferably from 5 to 30 parts bymass, to 100 parts by mass of the solid matter in the (E) high molecularweight epoxy group-containing resin.

By the addition of above-described crosslinking agent (curing agent),the (E) high molecular weight epoxy group-containing resin is fullycrosslinked. For further increasing the crosslinking performance at lowtemperatures, however, it is preferred to use a known curingacceleration catalyst. Examples of the curing acceleration catalyst areN-ethylmorphorine, dibutyltin dilaurate, cobalt naphthenate,tin(II)chloride, zinc naphtenate, and bismuth nitrate.

Aiming at the improvement of physical properties such as adhesion, tosome extent, a known resin such as acrylic, alkyd, and polyester resinscan be used together with the (E) high molecular weight epoxygroup-containing resin.

To improve the corrosion resistance, the top coating (coatingcomposition for top coating) according to the present invention maycontain a non-chromium based rust inhibitor, at need. By adding thenon-chromium based rust inhibitor to the top coating, further excellentcorrosion preventive performance is attained.

The non-chromium based rust inhibitor of one or more of thefollowing-given compounds (e1) through (e7) is particularly preferable.

-   -   (e1) silicon oxide    -   (e2) calcium and/or calcium compound    -   (e3) slightly-soluble phosphoric acid compound    -   (e4) molybdic acid compound    -   (e5) vanadium compound    -   (e6) organic compound containing S atom, being one or more        compounds selected from the group consisting of triazole, thiol,        thiaziazole, thiazole, and thiuram    -   (e7) organic compound containing N atom, being one or more        compounds selected from the group consisting of hydrazide        compound, pyrazole compound, triazole compound, tetrazole        compound, thiaziazole compound, and pyridazine compound.

The detail of these non-chromium based rust inhibitors (e1) through(e7), and their corrosion preventive mechanism are described beforerelating to the surface-treatment coating.

The blending quantity of the non-chromium based rust inhibitor ispreferably in a range from 0.1 to 50 parts by mass as solid matter to100 parts by mass of the resin solid matter in the coating compositionfor forming coating, more preferably from 0.5 to 30 parts by mass. Ifthe blending quantity of the non-chromium based rust inhibitor issmaller than 0.1 parts by mass, the effect of improvement in thecorrosion resistance after alkaline degreasing is insufficient, and ifthe blending quantity thereof exceeds 50 parts by mass, the coatability,the workability, and the weldability deteriorate, and further thecorrosion resistance deteriorates, both of which cases are notpreferable.

Two or more of the above (e1) through (e7) rust inhibitors may be addedin combination therewith. In that case, since the respective inherentcorrosion preventive actions are combined, stronger corrosion resistanceis attained. In particular, when the ingredient (e1) adopts a calciumion exchanged silica, and one or more of (e3) through (e7) ingredients,particularly all of the (e3) through (e7) ingredients, are added incombination, especially excellent corrosion resistance is attained.

Adding to the above rust inhibitor ingredients, the top coating (thecoating composition for top coating) may further contain one or more ofother oxide fine particles (aluminum oxide, zirconium oxide, titaniumoxide, cerium oxide, antimony oxide, and the like), phosphomolybdate(aluminum phosphomolybdate and the like), organic phosphoric acid and asalt thereof (phytic acid, phytinate, phosphonic acid, phosphonate,their metal salt, alkali metal salt, alkali earth metal salt, and thelike), and organic inhibitor (hydrazine derivative, thiol compound,dithiocarbamate, and the like), as the rust inhibitor.

Furthermore, at need, the top coating (coating composition for topcoating) may contain a solid lubricant to improve the workability of thecoating.

Examples of applicable solid lubricant in the present invention are thefollowing, which may be used separately or in combination of two or moreof them.

(1) Polyolefin wax, paraffin wax: for example, polyethylene wax,synthetic paraffin, natural paraffin, microwax, and chlorinatedhydrocarbon.

(2) Fluororesin fine particles: for example, polyfluoroethylene resin(polytetrafluoroethylene resin, and the like), polyvinylfluoride resin,polyvinylidenefluoride resin, and the like).

Other than those compounds, there may be applied one or more ofaliphatic amide-based compound (for example, stearic acid amide,palmitic acid amide, methylene bisstearoamide, ethylene bisstearoamide,oleic acid amide, acyl acid amides and alkylene bis fatty acid amide),metal soap (for example, calcium stearate, lead stearate, calciumlaurate, and calcium palmitate), metal sulfide (for example, molybdenumdisulfide and tungsten disulfide), graphite, graphite fluoride, boronnitride, polyalkyleneglycol, and alkali metal sulfide.

As of these solid lubricants, polyethylene wax and fluororesin fineparticles (particularly polytetrafluoroethylene resin fine particles)are preferred.

Examples of the applicable polyethylene wax are: Ceridust 9615A,Ceridust 3715, Ceridust 3620, and Ceridust 3910, (trade names;manufactured by Hoechst); Sun Wax 131-P and Sun Wax 161-P, (trade names;manufactured by Sanyo Chemical Industries, Ltd.) and CHEMIPEARL W-100,CHEMIPEARL W-200, CHEMIPEARL W-500, CHEMIPEARL W-800, and CHEMIPEARLW-950, (trade names; manufactured by Mitsui chemicals, Inc.)

For the fluororesin fine particles, tetrafluoroethylene fine particlesare the most preferable. Preferred tetrafluoroethylene fine particlesinclude: LubronL-2 and Lubron L-5, (trade names; manufactured by DaikinIndustries, Ltd.); MP1100 and MP1200, (trade names; manufactured byMitsui DuPont Co., Ltd.); and Fluon dispersion AD1, Fluon dispersionAD2, Fluon L141J, Fluon L150J, and Fluon L155J, (trade names;manufactured by Asahi ICI Fluoropolymers Co., Ltd.)

As of these, combined use of polyolefin wax and tetrafluoroethylene fineparticles is expected to provide particularly excellent lubricationeffect.

The blending quantity of the solid lubricant in the top coating is in arange from 1 to 10 part by mass as solid matter to 100 parts by mass ofthe resin solid matter in the coating composition for forming coating,more preferably from 1 to 10 parts by mass. If the blending quantity ofthe solid lubricant is smaller than 1 parts by mass, the effect oflubrication is poor, and if the blending quantity thereof exceeds 30parts by mass, the coatability deteriorates, both of which cases are notpreferable.

The top coating on the surface-treatment coating (coating compositionfor top coating) according to the present invention has the (E) highmolecular weight epoxy group-containing resin as an essentialingredient, and may contain, at need, a curing agent, a non-chromiumbased rust inhibitor, a solid lubricant, and the like. Furthermore, atneed, the top coating may contain one or more of organic coloringpigment (condensed polycyclic organic pigment, phthalocyanine-basedorganic pigment, and the like), coloring dye (azo-based dye soluble inorganic solvent, water-soluble azo-based metal dye, and the like),inorganic pigment (titanium oxide, and the like), conductive pigment(metal powder of zinc, aluminum, nickel, and the like, iron phosphide,antimony-doped tin oxide, and the like), chelating agent (thiol, and thelike), coupling agent (silane coupling agent, titanium coupling agent,and the like), and melamine-cyanuric acid additive, as the additives.

The above coating composition for forming coating, containing above mainingredient and additive ingredients, normally contains solvent (organicsolvent and/or water), and further contains, at need, neutralizer andthe like.

The above organic solvent is not specifically limited if only theorganic solvent allows the (E) high molecular weight epoxygroup-containing resin to be dissolved or dispersed, and is able toprepare the coating composition. For example, various organic solventsgiven in the above examples are applicable.

The neutralizer is added, at need, to neutralize and to make the (E)high molecular weight epoxy group-containing resin aquatic. If the (E)high molecular weight epoxy group-containing resin is a cationic resin,acetic acid, lactic acid, formic acid, and other acid can be used as theneutralizer.

The dry coating thickness of the top coating is in a range from 0.3 to2.0 μm, preferably from 0.4 to 1.5 μm. If the dry coating thickness issmaller than 0.3 μm, the corrosion resistance is insufficient, and ifthe dry coating thickness is larger than 2.0 μm, the weldability and theelectrocoatability deteriorate.

From the point of weldability and electrocoatability, the total coatingthickness of the primary surface-treatment coating with the secondarytop coating is preferably 2.0 μm or less.

The following is the description about the method for manufacturing thesurface-treated steel sheet according to the present invention.

To form the surface-treatment coating on the surface of a zinc-basedplated steel sheet or an aluminum-based plated steel sheet, the surfacetreatment coating composition (treatment solution) having the abovecomposition is applied onto the surface of the plated steel sheet so asthe dry coating thickness to become the above range, and then theapplied coating is heated to dry without washing with water.

The method for forming the surface treatment coating composition on thesurface of the plated steel sheet may be any of application method,immersion method, and spray method. The application method may be doneusing any of roll coater (3 roll type, 2 roll type, and the like),squeeze coater, and die coater. After the application treatment bysqueeze coater or the like, after the immersion treatment, or after thespray treatment, it is also possible to perform adjusting the coatingweight, uniformizing the appearance, and uniformizing the coatingthickness using air-knife method, roll-squeezing method, and the like.

After coating the surface treatment coating composition, the compositionis heated to dry without washing with water. The heating-drying methodmay be done by drier, hot-air furnace, high frequency induction heatingfurnace, infrared furnace, and the like. The heating-drying ispreferably conducted at ultimate sheet temperatures ranging from 30° C.to 150° C., more preferably from 40° C. to 140° C. If the heating-dryingtemperature is below 30° C., large amount of water is left in thecoating to result in insufficient corrosion resistance, and if theheating-drying temperature is above 150° C., the treatment becomesuneconomical, and the coating is defected to deteriorate the corrosionresistance. Furthermore, if the heating-drying temperature exceeds 150°C., the treatment cannot be used to BH steel sheets, which is notpreferable.

On thus formed surface-treatment coating, the top coating (organic resincoating) is formed as the secondary coating. That is, the coatingcomposition for the secondary coating is applied onto thesurface-treatment coating to above-described coating thickness, and thenis heated to dry. The application of the coating composition may be donein accordance with the method used for forming the surface-treatmentcoating.

After the application of the coating composition, normally the coatingcomposition is heated to dry without washing with water. However, thewater-washing step may be given after the application of the coatingcomposition. The heating-drying treatment may be given by drier, hot-airfurnace, high frequency induction heating furnace, infrared furnace, andthe like. The heating-drying is preferably conducted at ultimate sheettemperatures ranging from 30° C. to 150° C., more preferably from 40° C.to 140° C. If the heating-drying temperature is below 30° C., largeamount of water is left in the coating to result in insufficientcorrosion resistance, and if the heating-drying temperature is above150° C., the treatment becomes uneconomical, and the coating is defectedto deteriorate the corrosion resistance. In addition, if theheating-drying temperature exceeds 150° C., the treatment cannot be usedto BH steel sheets, which is not preferable.

Therefore, the method for manufacturing the surface-treated steel sheetaccording to the present invention and preferred embodiments for themanufacture are the following.

[1] A method for manufacturing surface-treated steel sheet withexcellent corrosion resistance contains the steps of: applying a surfacetreatment coating composition which contains ingredients (a) through (c)described below onto a surface of a zinc-based plated steel sheet or analuminum-based plated steel sheet, and then drying the applied surfacetreatment coating composition at ultimate sheet temperatures rangingfrom 30° C. to 150° C., thus forming a surface-treatment coating havingcoating thicknesses ranging from 0.01 to 1.0 μm; and forming a topcoating having coating thicknesses ranging from 0.3 to 2.0 μm on thesurface-treatment coating by applying a coating composition for topcoating containing an (E) high molecular weight epoxy group-containingresin having number average molecular weights ranging from 6000 to20000, and then drying the applied coating composition for top coatingat ultimate sheet temperatures ranging from 30° C. to 150° C.

(a) a water-epoxy resin dispersion which is prepared by dispersing inwater a resin obtained by a reaction of: an (A)polyalkyleneglycol-modified epoxy resin derived from a reaction ofpolyalkyleneglycol having number average molecular weights ranging from400 to 20000, a bisphenol type epoxy resin, an activehydrogen-containing compound, and a polyisocyanate compound; a (B) epoxygroup-containing resin other than the (A) polyalkyleneglycol-modifiedepoxy resin; and an active hydrogen-containing compound in which a partor entire of the compound is structured by a (C) hydrazine derivativehaving active hydrogen;

(b) a silane coupling agent at amounts ranging from 1 to 300 parts bymass of solid matter therein to 100 parts by mass of the resin solidmatter in the water-epoxy resin dispersion; and

(c) phosphoric acid and/or a hexafluorometal acid at amounts rangingfrom 0.1 to 80 parts by mass of solid matter therein to 100 parts bymass of the resin solid matter in the water-epoxy resin dispersion.

[2] The method for manufacturing surface-treated steel sheet withexcellent corrosion resistance according to [1], wherein the (C)hydrazine derivative containing active hydrogen is one or more compoundsselected from the group consisting of a pyrazole compound and a triazolecompound, which compound has a ring structure of five-membered ring orsix-membered ring, and has nitrogen atom in the ring structure.

[3] The method for manufacturing surface-treated steel sheet withexcellent corrosion resistance according to [1] or [2], wherein thesurface treatment coating composition for forming surface-treatmentcoating further contains a water-soluble phosphate at amounts rangingfrom 0.1 to 60 parts by mass of solid matter therein to 100 parts bymass of the resin solid matter in the water-epoxy resin dispersion ofthe ingredient (a).

[4] The method for manufacturing surface-treated steel sheet withexcellent corrosion resistance according to any of [1] through [3],wherein the surface treatment coating composition for formingsurface-treatment coating further contains a non-chromium based rustinhibitor at amounts ranging from 0.1 to 50 parts by mass of solidmatter therein to 100 parts by mass of the resin solid matter in thewater-epoxy resin dispersion of the ingredient (a).

[5] A method for manufacturing surface-treated steel sheet withexcellent corrosion resistance, which method has the steps of: applyinga surface treatment coating composition which contains ingredients (α)through (δ) described below onto a surface of a zinc-based plated steelsheet or an aluminum-based plated steel sheet, and then drying theapplied surface treatment coating composition at ultimate sheettemperatures ranging from 30° C. to 150° C., thus forming asurface-treatment coating having coating thicknesses ranging from 0.01to 1.0 μm; and forming a top coating having coating thicknesses rangingfrom 0.3 to 2.0 μm on the surface treatment coating by applying acoating composition for top coating containing an (E) high molecularweight epoxy group-containing resin having number average molecularweights ranging from 6000 to 20000, and then by drying the appliedcoating composition for top coating at ultimate sheet temperaturesranging from 30° C. to 150° C.:

(α) a water-epoxy resin dispersion which is prepared by dispersing inwater a (Z) modified epoxy resin obtained by a reaction of a (W) epoxygroup-containing resin, an (X) primary amine compound and/or secondaryamine compound, and an active hydrogen-containing compound in which apart or entire of the compound is structured by a (Y) hydrazinederivative having active hydrogen;

(β) a water dispersed polyurethane resine at amounts of mass ratio ofthe resin solid matter in the water-epoxy resin dispersion to the resinsolid matter in the water dispersed polyurethane resine, [water-epoxyresin dispersion]/[water dispersed polyurethane resine], ranging from95/5 to 5/95;

(γ) a silane coupling agent at amounts ranging from 1 to 300 parts bymass of solid matter therein to 100 parts by mass of the resin solidmatter in the water-epoxy resin dispersion; and

(δ) phosphoric acid and/or a hexafluorometal acid at amounts rangingfrom 0.1 to 80 parts by mass of solid matter therein to 100 parts bymass of the resin solid matter in the water-epoxy resin dispersion.

[6] The method for manufacturing surface-treated steel sheet withexcellent corrosion resistance according to [5], wherein the (Y)hydrazine derivative containing active hydrogen is one or more compoundsselected from the group consisting of a pyrazole compound and a triazolecompound, which compound has a ring structure of five-membered ring orsix-membered ring, and has a nitrogen atom in the ring structure.

[7] The method for manufacturing surface-treated steel sheet withexcellent corrosion resistance according to [5] or [6], wherein thesurface treatment coating composition for forming surface-treatmentcoating further contains a water-soluble phosphate at amounts rangingfrom 0.1 to 60 parts by mass of solid matter therein to 100 parts bymass of the resin solid matter in the sum of the water-epoxy resindispersion of the ingredient (α) and the water dispersed polyurethaneresine of the ingredient (β).

[8] The method for manufacturing surface-treated steel sheet withexcellent corrosion resistance according to any of [5] through [7],wherein the surface treatment coating composition for formingsurface-treatment coating further contains a non-chromium based rustinhibitor at amounts ranging from 0.1 to 50 parts by mass of solidmatter therein to 100 parts by mass of the resin solid matter in the sumof the water-epoxy resin dispersion of the ingredient (α) and the waterdispersed polyurethane resine of the ingredient (β).

[9] The method for manufacturing surface-treated steel sheet withexcellent corrosion resistance according to any of [1] through [8],wherein the coating composition for top coating further contains anon-chromium based rust inhibitor at amounts ranging from 0.1 to 50parts by mass of solid matter therein to 100 parts by mass of the resinsolid matter in the coating composition.

[10] The method for manufacturing surface-treated steel sheet withexcellent corrosion resistance according to any of [1] through [9],wherein the surface treatment coating composition for formingsurface-treatment coating and/or coating composition for top coatingcontain at one or more compounds selected from the group consisting of(e1) through (e7) given below as the non-chromium based rust inhibitor:

-   -   (e1) silicon oxide    -   (e2) calcium and/or calcium compound    -   (e3) slightly-soluble phosphoric acid compound    -   (e4) molybdic acid compound    -   (e5) vanadium compound    -   (e6) organic compound containing S atom, being one or more        compounds selected from the group consisting of triazole, thiol,        thiaziazole, thiazole, and thiuram    -   (e7) organic compound containing N atom, being one or more        compounds selected from the group consisting of hydrazide        compound, pyrazole compound, triazole compound, tetrazole        compound, thiaziazole compound, and pyridazine compound.

[11] The method for manufacturing surface-treated steel sheet withexcellent corrosion resistance according to any of [1] through [10],wherein the coating composition for top coating further contains acuring agent having a group which crosslinks with hydroxyl group, atamounts ranging from 1 to 50 parts by mass of solid matter therein to100 parts by mass of the solid matter in the (E) high molecular weightepoxy group-containing resin.

[12] The method for manufacturing surface-treated steel sheet withexcellent corrosion resistance according to [11], wherein the curingagent having a group crosslinking with hydroxyl group is an (F) aminoresin which has one or more imino groups as an average within a singlemolecule thereof.

[13] The method for manufacturing surface-treated steel sheet withexcellent corrosion resistance according to [11], wherein the curingagent having a group crosslinking with hydroxyl group is a (G)polyisocyanate compound which has four or more isocyanate groups as anaverage within a single molecule thereof.

[14] The method for manufacturing surface-treated steel sheet withexcellent corrosion resistance according to [13], wherein the (G)polyisocyanate compound is the one in which at least some of theisocyanate groups in the polyisocyanate compound are blocked by ablocking agent.

[15] The method for manufacturing surface-treated steel sheet withexcellent corrosion resistance according to any of [1] through [14],wherein the (E) high molecular weight epoxy group-containing resin inthe coating composition for top coating is a modified epoxygroup-containing resin which is modified by an (H) activehydrogen-containing compound in which a part or entire of the compoundis structured by an (I) hydrazine derivative having active hydrogen.

[16] The method for manufacturing surface-treated steel sheet withexcellent corrosion resistance according to any of [1] through [15],wherein the coating composition for top coating further contains a solidlubricant at amounts ranging from 1 to 30 parts by mass of solid mattertherein to 100 parts by mass of the resin solid matter in the coatingcomposition.

The surface-treatment coating and the top coating may be formed oneither of a single side or both sides of the plated steel sheet. Thecombination of the coating configuration on the front side and the rearside of the plated steel sheet is arbitrary, including(surface-treatment coating+top coating)/(non-treatment),(surface-treatment coating+top coating)/(surface-treatment coating),(surface-treatment coating+top coating)/(surface-treatment coating+topcoating)

EXAMPLE 1

Table 1 shows the plated steel sheets used. The surface treatmentcoating compositions for forming the primary coating adopted therespective water-soluble or water-dispersible epoxy resins given inTable 2 as the resin compositions. To the resin compositions, therespective appropriate quantities of silane coupling agents (Table 3),phosphoric acid or hexafluorometal acids (Table 4,), water-solublephosphates (Table 5), and non-chromium based rust inhibitors (Table 6)were added. Each of the mixtures was agitated in a disperser for coating(sand-grinder) for a specified time to prepare the surface treatmentcoating composition.

The water-soluble or water-dispersible epoxy resins given in Table 2were prepared by the following procedure.

Preparation of Polyalkyleneglycol-modified Epoxy Resin

MANUFACTURE EXAMPLE 1

To a four-neck flask equipped with a thermometer, an agitator, and acooling tube, 1688 g of polyethyleneglycol having a number averagemolecular weight of 4000, and 539 g of methylethylketone were charged.The mixture was agitated at 60° C. to bring the mixture homogeneous andtransparent. After that, 171 g of tolylenediisocyanate was added to themixture to conduct reaction for 2 hours. Then, 1121 g of Epicoat 834×90(an epoxy resin having an epoxy equivalent of 250; manufactured by ShellJapan Ltd.), 66 g of diethyleneglycol ethylether, and 1.1 g of 1%dibutyltin dilaurate solution were added to the mixture to furtherconduct reaction for 2 hours. After that, the mixture was heated to 80°C. to conduct reaction for 3 hours to confirm that the isocyanate valuebecame 0.9 or lower. Then, the mixture was heated to 90° C. to conductdistillation under a reduced pressure to remove methylethylketone toreach the solid matter concentration to 81.7%. After removing themethylethylketone, 659 g of propyleneglycol monomethylether and 270 g ofdeionized water were added to dilute the mixture, thus obtained thepolyalkyleneglycol-modified epoxy resin solution A1 containing solidmatter of 76%.

Preparation of Water-Epoxy Resin Dispersion

MANUFACTURE EXAMPLE 2

To a four-neck flask, 2029 g of EP1004 (an epoxy resin having a numberaverage molecular weight of 1000; manufactured by Yuka-Shell Epoxy Co.,Ltd.), and 697 g of propyleneglycol monobutylether were charged. Themixture was heated to 110° C. to completely dissolve the epoxy resinwithin 1 hour. Then, 1180 g of the polyalkyleneglycol-modified epoxyresin solution A1 prepared in Manufacture Example 1, and 311.7 g of3-amino-1,2,4-triazole (molecular weight of 84) were added to themixture, and thus prepared mixture was heated to conduct reaction at100° C. for 5 hours. After that, 719.6 g of propyleneglycolmonobutylether was added to the mixture to obtain the resin solution D1.

A 257.6 g aliquot of the resin solution D1 was mixed with 50 g ofMF-K60X (an isocyanate curing agent; manufactured by Asahi ChemicalIndustry Co., Ltd.), and 0.3 g of Scat24 (a curing catalyst). Afterfully agitated the mixture, 692.1 g of water was dropped gradually tomix and agitate the mixture, thus obtained the water-epoxy resindispersion E1.

MANUFACTURE EXAMPLE 3 Water-Epoxy Resin Dispersion Containing NoHydrazine Derivative

To a four-neck flask, 2029 g of EP1004 (an epoxy resin having a numberaverage molecular weight of 1000; manufactured by Yuka-Shell Epoxy Co.,Ltd.), and 697 g of propyleneglycol monobutylether were charged. Themixture was heated to 110° C. to completely dissolve the epoxy resinwithin 1 hour. Then, 1180 g of the polyalkyleneglycol-modified epoxyresin solution A1 prepared in Manufacture Example 1, and 527.0 g ofpropyleneglycol monobutylether were added to the mixture to obtain theresin solution D2.

A 257.6 g aliquot of the resin solution D2 was mixed with 50 g ofMF-K60X (an isocyanate curing agent; manufactured by Asahi ChemicalIndustry Co., Ltd.), and 0.3 g of Scat24 (a curing catalyst). Afterfully agitated the mixture, 692.1 g of water was dropped gradually tomix and agitate the mixture, thus obtained the water-epoxy resindispersion E2.

The coating composition for forming the secondary coating adopted therespective resin compositions given in Table 7 and Table 8, to whichfurther added appropriately the respective non-chromium based rustinhibitors (Table 6) and solid lubricators (Table 9). Each of themixtures was agitated in a disperser for coating (sand-grinder) for aspecified time to prepare the surface treatment coating composition.

The base resins (reaction products) of the resin compositions given inTable 7 and Table 8 were synthesized by the following procedure.

SYNTHESIS EXAMPLE 1

To a four-neck flask, 634 parts of Epicoat 828 (epoxy equivalent of 187;manufactured by Japan Epoxy Resins Co., Ltd.), 366 parts of Bisphenol-A,8 parts of 50% tetraethylammoniumbromide aqueous solution, and 180 partsof cyclohexane were charged. The mixture was heated to 150° C. toconduct reaction for 5 hours. After that, 300 parts ofmethylisobutylketone and 1843 parts of cyclohexanone were added whilecooling the mixture to obtain the epoxy resin solution F1 with solidmatter of 30%, (resin composition (1)). The resin had the number averagemolecular weight of 7600.

SYNTHESIS EXAMPLE 2

To a four-neck flask, 347 parts of Epicoat 1256 (epoxy equivalent of7880; manufactured by Japan Epoxy Resins Co., Ltd.), and 543 parts ofcyclohexane were charged. The mixture was heated to 130° C. to fullydissolve the epoxy resin within 2 hours. The mixture was cooled to 120°C. Then, 3.7 parts of 3-amino-1,2,4-tolyazole (molecular weight of 84)was added to the mixture to conduct reaction for 6 hours until the epoxygroup vanished. After that, 78 parts of methylisobutylketone and 197parts of cyclohexanone were added while cooling the mixture to obtainthe triazole-modified epoxy resin solution F2 with solid matter of 30%,(resin composition (2)). The resin had the number average molecularweight of 10100.

SYNTHESIS EXAMPLE 3

To a four-neck flask, 637 parts of Epicoat 828 (epoxy equivalent of 187;manufactured by Japan Epoxy Resins Co., Ltd.) 363 parts of Bisphenol-A,10 parts of 50% tetraethylammonium bromide aqueous solution, and 175parts of cyclohexane were charged. The mixture was heated to 160° C. toconduct reaction for 4 hours, thus obtained an epoxy resin solution withsolid matter of 85%. Then, 1315 pars of cyclohexanone was added to themixture, and then the mixture was cooled to 100° C. Further 9.7 parts of3,5-dimethylpyrazole and 13 parts of dibutylamine were added to themixture to conduct reaction for 6 hours until the epoxy group vanished.After that, 908 parts of methylisobutylketone was added to the mixturewhile cooling the mixture to obtain the pyrazole-modified epoxy resinsolution F3 with solid matter of 30%, (resin composition (3)) The resinhad the number average molecular weight of 6300.

SYNTHESIS EXAMPLE 4

To a four-neck flask, 1833 parts of Epicoat 828 (epoxy equivalent of187; manufactured by Japan Epoxy Resins Co., Ltd.) 894 parts ofBisphenol-A, 1.96 parts of tetraethylammoniumbromide, and 294 parts ofmethylisobutylketone were charged. The mixture was heated to 140° C. toconduct reaction for 4 hours. Then, 3795 parts of ethyleneglycolmonobutylether was added to the mixture while cooling the mixture, thusobtained the epoxy resin solution F4 (epoxy equivalent of 1388, andsolid matter of 40%), (resin composition (4)). The resin had the numberaverage molecular weight of 3100.

As the treating base sheets, the plated steel sheets given in Table 1,which are the plated steel sheets with cold-rolled steel sheets as thebase sheets, were adopted. The plated steel sheets are for householdelectric appliances, building materials, and automobile parts. Thethickness of the steel sheets was selected responding to the objectivesof evaluations. After alkali degreasing, washing with water, and dryingon the surface of the plated steel sheets, the above-describedrespective surface treatment coating compositions for forming theprimary coating were applied using a roll coater, and then thecompositions were heated to dry at various temperatures. The coatingthickness was adjusted by the solid matter content (heating residue) ofthe surface treatment coating composition or by the applicationconditions (roll pressing force, rotational speed, and the like)

Then, the respective coating compositions for forming the secondarycoating were applied using a roll coater, and were heated to dry atvarious temperatures. The coating thickness was adjusted by the solidmatter content (heating residue) of the surface treatment coatingcomposition or by the application conditions (roll pressing force,rotational speed, and the like)

Tables 10 through 25 show the result of evaluation of thus preparedsurface-treated steel sheets in terms of coating composition and qualityperformance (corrosion resistance, corrosion resistance after forming,weldability, and electrodeposited paint adhesion). The evaluation ofquality was given in the following procedure.

(1) Corrosion Resistance

Each sample was degreased by FC-4460 (manufactured by Japan ParkerizingCo., Ltd.) under the condition of 60° C. for 2 minutes. Then, the samplewas subjected to the following-given combined cycle test (CCT) toevaluate the corrosion resistance based on the area percentage of whiterust generation and the area percentage of red rust generation after 50cycles.

The evaluation criterion is the following.

-   ⊚: less than 5% of the area percentage of white rust generation-   ◯+: 5% or more and less than 10% of the area percentage of white    rust generation-   ◯: 10% or more and less than 30% of the area percentage of white    rust generation-   ◯−: 30% or more of the area percentage of white rust generation,    without red rust generation-   Δ: with red rust generation, less than 10% of area percentage of red    rust generation-   X: 10% or more of area percentage of red rust generation    (2) Corrosion Resistance After Forming

Each sample was subjected to deformation and sliding with a draw-beadunder the condition given below. Thus treated sample was degreased byFC-4460 (manufactured by Japan Parkerizing Co., Ltd.) under thecondition of 60° C. for 2 minutes. Then, the sample was treated by CCTgiven in the “(1) Corrosion resistance” to evaluate the corrosionresistance after forming based on the area percentage of white rustgeneration and the area percentage of red rust generation after 36cycles.

-   Pressing load: 800 kgf-   Draw-out speed: 1000 mm/min-   Bead shoulder R: 2 mm on male side, 3 mm on female side-   Penetration depth: 7 mm-   Oil: Pleton R-352L; manufactured by Sugimura Chemical Industry, Co.,    Ltd.    The evaluation criterion is the following.-   ⊚: less than 5% of the area percentage of white rust generation-   ◯+: 5% or more and less than 10% of the area percentage of white    rust generation-   ◯: 10% or more and less than 30% of the area percentage of white    rust generation-   ◯−: 30% or more of the area percentage of white rust generation,    without red rust generation-   Δ: with red rust generation, less than 10% of area percentage of red    rust generation-   X: 10% or more of area percentage of red rust generation    (3) Weldability

Each sample was tested by welding to evaluate in terms of successivespottability using a CF type Cr—Cu electrode at 200 kg of pressingforce, 10 cycles/50 Hz of power applying time, and 10 kA of weldingcurrent. The evaluation was given by the number of successive spots. Theevaluation criterion is the following.

-   ⊚: 2000 or larger number of spots-   ◯: 1000 or more and less than 2000 of the number of spots-   Δ: 500 or more and less than 1000 of the number of spots-   X: less than 500 of the number of spots    (4) Electrodeposited Paint Adhesion

Each sample was coated by a cationic electrodeposition coat GT-10(manufactured by Kansai Paint Co., Ltd.) to a coating thickness of 30μm. The coating was then baked at 130° C. for 30 minutes. The coatedsample was immersed in boiling water for 2 hours, and then immediatelysubjected to cross-cut corrosion test (10×10 segments, 1 mm in spacing)applying/peeling adhesion tapes, thus determined the peeling areapercentage on the coating.

The evaluation criterion is the following.

-   ⊚: no peeling occurred-   ◯: less than 5% of peeling area percentage-   Δ: 5% or more and less than 20% of peeling area percentage-   X: 20% or more of peeling area percentage

TABLE 1 Coating No. Plated steel sheet weight (g/m²) 1Electro-galvanized steel sheet 50 2 Hot-dip galvanized steel sheet 60 3Alloyed hot-dip galvanized steel sheet 45 (Fe: 10 mass %) 4 Zn—Ni alloyplated steel sheet (Ni: 12 mass %) 20 5 Hot-dip Zn—Al alloy plated steelsheet 90 (Al: 55 mass %) 6 Hot-dip Zn—5 mass % Al—0.5 mass % Mn alloy 90plated steel sheet 7 Hot-dip aluminum plated steel sheet (Al—Si 60alloy, Si: 6 mass %) 8 Zn—Al—Mg alloy plated steel sheet 120 (Al: 6 mass%, Mg: 3 mass %) 9 Hot-dip Zn—Mg alloy plated steel sheet 150 (Mg: 0.5mass %)

TABLE 2 No. Water-soluble or water-dispersible epoxy resin 1 E1 of(Manufacture Example 2) given in the description 2 D1 of (ManufactureExample 2) given in the description 3 A1 of (Manufacture Example 1)given in the description 4 D2 of (Manufacture Example 3) given in thedescription 5 E2 of (Manufacture Example 3) given in the description

TABLE 3 No. Silane coupling agent Product name 1 γ-aminopropyltriethoxysilane “KBE-903”, manufactured by Shin-Etsu Chemical Co., Ltd.2 γ-aminopropyl trimethoxysilane “KBM-903”, manufactured by Shin-EtsuChemical Co., Ltd. 3 N-β (aminoethyl) “KBM-602”, manufacturedγ-aminopropylmethyl by Shin-Etsu dimethoxysilane Chemical Co., Ltd. 4N-β (aminoethyl) γ-aminopropyl “KBM-603”, manufactured trimethoxysilaneby Shin-Etsu Chemical Co., Ltd. 5 N-β (aminoethyl) γ-aminopropyl“KBE-603”, manufactured triethoxysilane by Shin-Etsu Chemical Co., Ltd.6 γ-glycidoxypropyl trimethoxysilane “KBM-403”, manufactured byShin-Etsu Chemical Co., Ltd. 7 γ-glycidoxypropylmethyl “KBE-402”,manufactured diethoxysilane by Shin-Etsu Chemical Co., Ltd. 8γ-glycidoxypropyl triethoxysilane “KBE-403”, manufactured by Shin-EtsuChemical Co., Ltd.

TABLE 4 No. Kind 1 Phosphoric acid 2 Hexafluorosilicate (hydrofluosilicacid) H₂SiF₆ 3 Hexafluorotitanate H₂TiF₆ 4 Hexafluorozirconate H₂ZrF₆

TABLE 5 No. Water-soluble phosphate 1 Aluminum phosphate([Cation]/[P₂O₅] = 0.90) 2 Manganese phosphate ([Cation]/[P₂O₅] = 0.77)3 Magnesium phosphate ([Cation]/[P₂O₅] = 0.97) 4 Nickel phosphate([Cation]/[P₂O₅] = 0.82)

TABLE 6 No. Rust inhibitor 1 Calcium ion exchanged silica 2 Colloidalsilica 3 Fumed silica 4 Aluminum dihydrogen tripolyphosphate 5 Aluminumphosphomolybdate 6 Tetraethylthiuram disulfide 7 Vanadyl sulfate

TABLE 7 Base resin Curing agent Suitability to the conditions No. Kind*1 Blending quantity Kind *2 Blending quantity Catalyst of the invention1 (1) 100 parts A  5 parts Dibutyltin dilaurate (0.2 parts) Satisfied 2(1) 100 parts B 25 parts Dibutyltin dilaurate (1.0 part) Satisfied 3 (1)100 parts C 25 parts — Satisfied 4 (5) 100 parts A 10 parts Dibutyltindilaurate (2.0 parts) Satisfied 5 (5) 100 parts B 40 parts Dibutyltindilaurate (3.0 parts) Satisfied 6 (5) 100 parts C 50 parts Dibutyltindilaurate (4.0 parts) Satisfied 7 (2) 100 parts A 25 parts Cobaltnaphthenate (1.0 part) Satisfied 8 (2) 100 parts B  5 parts Tin(II)chloride (1.0 part) Satisfied 9 (2) 100 parts C 40 partsN-ethylmorpholine (1.0 part) Satisfied 10 (3) 100 parts A 10 partsCobalt naphthenate (0.5 parts) Satisfied 11 (3) 100 parts B 25 partsCobalt naphthenate (1.0 part) Satisfied 12 (3) 100 parts C  5 partsCobalt naphthenate (2.0 parts) Satisfied 13 (4) 100 parts A 25 partsTin(II) chloride (0.5 parts) Not satisfied 14 (4) 100 parts B 25 partsTin(II) chloride (2.0 parts) Not satisfied *1: The resin compositions(1) through (4) which were synthesized in the respective SynthesisExamples 1 through 4 given in the description of the invention, and theresin compositions (5) through (7) given below. (5): High molecularweight bisphenol-based epoxy resin (Phenoxy resin): “Epicoat 1256”,manufactured by Japan Epoxy Resins Co., Ltd.; number average molecularweight 10000. (6): Branched polyester resin: “Biron GK-130”,manufactured by ToyoboCo., Ltd.; number average molecular weight 7000.(7): High molecular weight polyester resin: “Biron GK-140”, manufacturedby Toyobo Co., Ltd.; number average molecular weight 13000. *2 A: MEKoxime-blocked IPDI: “Takenate B-870N”, manufactured by Takeda ChemicalIndustries, Ltd.; the number of isocyanate groups in a molecule: 3 B:Isocyanurate type: “DESMODURE BL-3175”, manufactured by Bayer; thenumber of isocyanate groups in a molecule: 3 C: MEK oxime-blocked HMDI:“Duranate MF-B80M”, manufactured by Asahi Chemical Industry Co., Ltd.;the number of isocyanate groups in a molecule: 6 D: Imino-group typemelamine resin:“Cymel 325”, manufactured by Mitsui Cytec, Ltd. E: Allmethoxy group type melamine resin: “Cymel 303”, manufactured by MitsuiCytec, Ltd.

TABLE 8 Base resin Curing agent Suitability to the conditions No. Kind*1 Blending quantity Kind *2 Blending quantity Catalyst of the invention15 (4) 100 parts C 40 parts N-ethylmorpholine (2.0 parts) Not satisfied16 (1) 100 parts D 20 parts — Satisfied 17 (5) 100 parts D 40 parts —Satisfied 18 (3) 100 parts D 10 parts — Satisfied 19 (4) 100 parts D 20parts — Not satisfied 20 (1) 100 parts E 20 parts Dodecylbenzenesulfonate (1.0 pat) Satisfied 21 (6) 100 parts C 20 parts — Notsatisfied 22 (7) 100 parts C 25 parts Dibutyltin dilaurate (2.0 parts)Not satisfied 23 (7) 100 parts D 10 parts — Not satisfied *1: The resincompositions (1) through (4) which were synthesized in the respectiveSynthesis Examples 1 through 4 given in the description of theinvention, and the resin compositions (5) through (7) given below. (5):High molecular weight bisphenol-based epoxy resin (Phenoxy resin):“Epicoat 1256”, manufactured by Japan Epoxy Resins Co., Ltd.; numberaverage molecular weight 10000. (6): Branched polyester resin: “BironGK-130”, manufactured by ToyoboCo., Ltd.; number average molecularweight 7000. (7): High molecular weight polyester resin: “Biron GK-140”,manufactured by Toyobo Co., Ltd.; number average molecular weight 13000.*2 A: MEK oxime-blocked IPDI: “Takenate B-870N”, manufactured by TakedaChemical Industries, Ltd.; the number of isocyanate groups in amolecule: 3 B: Isocyanurate type: “DESMODURE BL-3175”, manufactured byBayer; the number of isocyanate groups in a molecule: 3 C: MEKoxime-blocked HMDI: “Duranate MF-B80M”, manufactured by Asahi ChemicalIndustry Co., Ltd.; the number of isocyanate groups in a molecule: 6 D:Imino-group type melamine resin:“Cymel 325”, manufactured by MitsuiCytec, Ltd. E: All methoxy group type melamine resin: “Cymel 303”,manufactured by Mitsui Cytec, Ltd.

TABLE 9 No. Solid lubricant Product name 1 Polyethylene wax “LUVAX1151”,manufactured by Nippon Seiro Co., Ltd. 2 Polyethylene wax“Ceridust3620”, manufactured by Hoechst 3 Tetrafluoroethylene fine“MP1100”, manufactured particles by Mitsui DuPont KK.Symbols *1 through *10 found in Tables 10 through 25 designate thefollowing, respectively.

-   *1: No. given in Table 1, (plated steel sheet)-   *2: No. given in Table 2, (water-dispersible epoxy resin)-   *3: No. given in Table 3, (silane coupling agent)-   *4: No. given in Table 4, (phosphoric acid or hexafluorometal acid)-   *5: No. given in Table 5, (water-soluble phosphate)-   *6: No. given in Table 6, (rust inhibitor)-   *7: Parts by mass, (for the ingredients other than water-soluble or    water-dispersible epoxy resin, parts by mass to 100 parts by mass of    the solid matter in the water-soluble or water-dispersible epoxy    resin)-   *8: No. given in Table 7 and 8, (resin composition)-   *9: No. given in Table 9, (solid lubricant)-   *10: Parts by mass (for the generatio other than organic resin,    parts by mass to 100 parts by mass of the solid matter in the    organic resin)

TABLE 10 Primary layer Water-soluble resin or water-dispersible SilanePhosphoric acid or Water-soluble Plated resin coupling agenthexafluorometal acid phosphate steel Blending Blending Blending BlendingClassification No. sheet *1 Kind *2 quantity *7 Kind *3 quantity *7 Kind*4 quantity *7 Kind *5 quantity *7 Comparative 1 1 — — 1 25 1 40 — —example Comparative 2 1 1 100 — — 1 40 — — example Example 3 1 1 100 1 51 40 — — Example 4 1 1 100 1 15 1 40 — — Example 5 1 1 100 1 50 1 40 — —Example 6 1 1 100 1 100 1 40 — — Comparative 7 1 1 100 1 500 1 40 — —example Comparative 8 1 1 100 1 25 — — — — example Example 9 1 1 100 125 1 1 — — Example 10 1 1 100 1 25 1 5 — — Example 11 1 1 100 1 25 1 20— — Example 12 1 1 100 1 25 1 40 — — Comparative 13 1 1 100 1 25 1 100 —— example Example 14 1 1 100 1 25 1 40 1 0.5 Example 15 1 1 100 1 25 140 1 5 Example 16 1 1 100 1 25 1 40 1 10 Primary layer Coating Rustinhibitor thickness Baking Classification Kind *6 Blending quantity *7(μm) temperature (° C.) Comparative — — 0.3 140 example Comparative — —0.3 140 example Example — — 0.3 140 Example — — 0.3 140 Example — — 0.3140 Example — — 0.3 140 Comparative — — 0.3 140 example Comparative — —0.3 140 example Example — — 0.3 140 Example — — 0.3 140 Example — — 0.3140 Example — — 0.3 140 Comparative — — 0.3 140 example Example — — 0.3140 Example — — 0.3 140 Example — — 0.3 140

TABLE 11 Secondary layer Organic resin Rust inhibitor Solid lubricantCoating Baking Blending Blending Blending thickness temperatureClassification No. Kind *8 quantity *10 Kind *6 quantity *10 Kind *9quantity *10 (μm) (° C.) Comparative 1 1 100 1 20 — — 1.0 140 exampleComparative 2 1 100 1 20 — — 1.0 140 example Example 3 1 100 1 20 — —1.0 140 Example 4 1 100 1 20 — — 1.0 140 Example 5 1 100 1 20 — — 1.0140 Example 6 1 100 1 20 — — 1.0 140 Comparative 7 1 100 1 20 — — 1.0140 example Comparative 8 1 100 1 20 — — 1.0 140 example Example 9 1 1001 20 — — 1.0 140 Example 10 1 100 1 20 — — 1.0 140 Example 11 1 100 1 20— — 1.0 140 Example 12 1 100 1 20 — — 1.0 140 Comparative 13 1 100 1 20— — 1.0 140 example Example 14 1 100 1 20 — — 1.0 140 Example 15 1 100 120 — — 1.0 140 Example 16 1 100 1 20 — — 1.0 140 Performance Corrosionresistance after Electrodeposited Classification Corrosion resistancetreatment Weldability paint adhesion Comparative Δ X ⊚ ⊚ exampleComparative ◯ X ⊚ ⊚ example Example ◯ ◯− ⊚ ⊚ Example ◯ ◯ ⊚ ⊚ Example ◯ ◯⊚ ⊚ Example ◯ ◯ ⊚ ⊚ Comparative Δ X ◯ ◯ example Comparative X X ⊚ ⊚example Example ◯ ◯− ⊚ ⊚ Example ◯ ◯ ⊚ ⊚ Example ◯ ◯ ⊚ ⊚ Example ◯ ◯ ⊚ ⊚Comparative Δ X ⊚ ⊚ example Example ◯ ◯ ⊚ ⊚ Example ◯ ◯ ⊚ ⊚ Example ◯ ◯⊚ ⊚

TABLE 12 Primary layer Water-soluble resin or water-dispersible SilanePhosphoric acid or Water-soluble Plated resin coupling agenthexafluorometal acid phosphate steel Blending Blending Blending BlendingClassification No. sheet *1 Kind *2 quantity *7 Kind *3 quantity *7 Kind*4 quantity *7 Kind *5 quantity *7 Example 17 1 1 100 1 25 1 40 1 30Comparative 18 1 1 100 1 25 1 40 1 80 example Example 19 1 1 100 1 25 140 — — Example 20 1 1 100 1 25 1 40 — — Example 21 1 1 100 1 25 1 40 — —Example 22 1 1 100 1 25 1 40 — — Example 23 1 1 100 1 25 1 40 1 5Example 24 1 1 100 1 25 1 40 1 5 Example 25 1 1 100 1 25 1 40 1 10Example 26 1 1 100 1 25 1 40 1 10 Comparative 27 1 1 100 1 25 1 40 1 5example Example 28 1 1 100 1 25 1 40 1 5 Example 29 1 1 100 1 25 1 40 15 Example 30 1 1 100 1 25 1 40 1 5 Example 31 1 1 100 1 25 1 40 1 5Primary layer Coating Rust inhibitor thickness Baking ClassificationKind *6 Blending quantity *7 (μm) temperature (° C.) Example — — 0.3 140Comparative — — 0.3 140 example Example 1 0.5 0.3 140 Example 1 10 0.3140 Example 1 30 0.3 140 Example 1 70 0.3 140 Example 1 0.5 0.3 140Example 1 10 0.3 140 Example 1 10 0.3 140 Example 1 30 0.3 140Comparative 1 10 0.005 140 example Example 1 10 0.01 140 Example 1 100.1 140 Example 1 10 0.6 140 Example 1 10 1.0 140

TABLE 13 Secondary layer Organic resin Rust inhibitor Solid lubricantCoating Baking Blending Blending Blending thickness temperatureClassification No. Kind *8 quantity *10 Kind *6 quantity *10 Kind *9quantity *10 (μm) (° C.) Example 17 1 100 1 20 — — 1.0 140 Comparative18 1 100 1 20 — — 1.0 140 example Example 19 1 100 1 20 — — 1.0 140Example 20 1 100 1 20 — — 1.0 140 Example 21 1 100 1 20 — — 1.0 140Example 22 1 100 1 20 — — 1.0 140 Example 23 1 100 1 20 — — 1.0 140Example 24 1 100 1 20 — — 1.0 140 Example 25 1 100 1 20 — — 1.0 140Example 26 1 100 1 20 — — 1.0 140 Comparative 27 1 100 1 20 — — 1.0 140example Example 28 1 100 1 20 — — 1.0 140 Example 29 1 100 1 20 — — 1.0140 Example 30 1 100 1 20 — — 1.0 140 Example 31 1 100 1 20 — — 1.0 140Performance Corrosion resistance after Electrodeposited ClassificationCorrosion resistance treatment Weldability paint adhesion Example ◯ ◯ ⊚⊚ Comparative Δ Δ ⊚ ⊚ example Example ⊚ ◯ ⊚ ⊚ Example ⊚ ◯ ⊚ ⊚ Example ⊚◯ ◯ ⊚ Example ◯   ◯− ◯ ⊚ Example ⊚ ◯ ⊚ ⊚ Example ◯+ ◯− ⊚ ⊚ Example ⊚ ◯+⊚ ⊚ Example ⊚ ◯ ◯ ⊚ Comparative X X ⊚ ⊚ example Example ◯− ◯− ⊚ ⊚Example ◯ ◯ ⊚ ⊚ Example ◯+ ◯− ◯ ◯ Example ◯+ ◯− ◯ ◯

TABLE 14 Primary layer Water-soluble resin or water-dispersible SilanePhosphoric acid or Water-soluble Plated resin coupling agenthexafluorometal acid phosphate steel Blending Blending Blending BlendingClassification No. sheet *1 Kind *2 quantity *7 Kind *3 quantity *7 Kind*4 quantity *7 Kind *5 quantity *7 Comparative 32 1 1 100 1 25 1 40 1 5example Comparative 33 1 1 100 1 25 1 40 1 5 example Example 34 1 1 1001 25 1 40 1 5 Example 35 1 1 100 1 25 1 40 1 5 Example 36 1 1 100 1 25 140 1 5 Example 37 2 1 100 1 25 1 40 1 5 Example 38 3 1 100 1 25 1 40 1 5Example 39 4 1 100 1 25 1 40 1 5 Example 40 5 1 100 1 25 1 40 1 5Example 41 6 1 100 1 25 1 40 1 5 Example 42 7 1 100 1 25 1 40 1 5Example 43 8 1 100 1 25 1 40 1 5 Example 44 9 1 100 1 25 1 40 1 5Comparative 45 1 2 100 1 25 1 40 1 5 example Comparative 46 1 3 100 1 251 40 1 5 example Primary layer Coating Rust inhibitor thickness BakingClassification Kind *6 Blending quantity *7 (μm) temperature (° C.)Comparative 1 10 1.5 140 example Comparative 1 10 0.3 25 example Example1 10 0.3 50 Example 1 10 0.3 100 Example 1 10 0.3 200 Example 1 10 0.3140 Example 1 10 0.3 140 Example 1 10 0.3 140 Example 1 10 0.3 140Example 1 10 0.3 140 Example 1 10 0.3 140 Example 1 10 0.3 140 Example 110 0.3 140 Comparative 1 10 0.3 140 example Comparative 1 10 0.3 140example

TABLE 15 Secondary layer Organic resin Rust inhibitor Solid lubricantCoating Baking Blending Blending Blending thickness temperatureClassification No. Kind *8 quantity *10 Kind *6 quantity *10 Kind *9quantity *10 (μm) (° C.) Comparative 32 1 100 1 20 — — 1.0 140 exampleComparative 33 1 100 1 20 — — 1.0 140 example Example 34 1 100 1 20 — —1.0 140 Example 35 1 100 1 20 — — 1.0 140 Example 39 1 100 1 20 — — 1.0140 Example 37 1 100 1 20 — — 1.0 140 Example 38 1 100 1 20 — — 1.0 140Example 39 1 100 1 20 — — 1.0 140 Example 40 1 100 1 20 — — 1.0 140Example 41 1 100 1 20 — — 1.0 140 Example 42 1 100 1 20 — — 1.0 140Example 43 1 100 1 20 — — 1.0 140 Example 44 1 100 1 20 — — 1.0 140Comparative 45 1 100 1 20 — — 1.0 140 example Comparative 46 1 100 1 20— — 1.0 140 example Performance Corrosion resistance afterElectrodeposited Classification Corrosion resistance treatmentWeldability paint adhesion Comparative ⊚ ⊚ X X example Comparative Δ Δ ⊚⊚ example Example   ◯−   ◯− ⊚ ⊚ Example ◯ ◯ ⊚ ⊚ Example   ◯−   ◯− ⊚ ⊚Example   ◯+   ◯+ ◯ ⊚ Example ◯ ◯ ⊚ ⊚ Example ⊚ ⊚ ◯ ◯ Example ⊚ ⊚ ◯ ◯Example ⊚ ⊚ ◯ ◯ Example ⊚ ◯+ ◯ ◯ Example ⊚ ⊚ ◯ ◯ Example ⊚ ⊚ ◯ ◯Comparative ◯ ◯ ⊚ ⊚ example Comparative ◯ ◯ ⊚ ⊚ example

TABLE 16 Primary layer Water-soluble resin or water-dispersible SilanePhosphoric acid or Water-soluble Plated resin coupling agenthexafluorometal acid phosphate steel Blending Blending Blending BlendingClassification No. sheet *1 Kind *2 quantity *7 Kind *3 quantity *7 Kind*4 quantity *7 Kind *5 quantity *7 Comparative 47 1 4 100 1 25 1 40 1 5example Comparative 48 1 5 100 1 25 1 40 1 5 example Example 49 1 1 1002 25 1 40 1 5 Example 50 1 1 100 3 25 1 40 1 5 Example 51 1 1 100 4 25 140 1 5 Example 52 1 1 100 5 25 1 40 1 5 Example 53 1 1 100 6 25 1 40 1 5Example 54 1 1 100 7 25 1 40 1 5 Example 55 1 1 100 8 25 1 40 1 5Example 56 1 1 100 1 25 2 40 1 5 Example 57 1 1 100 1 25 3 40 1 5Example 58 1 1 100 1 25 4 40 1 5 Example 59 1 1 100 1 25 1 40 2 5Example 60 1 1 100 1 25 1 40 3 5 Example 61 1 1 100 1 25 1 40 4 5Example 62 1 1 100 1 25 1 40 1 5 Primary layer Coating Rust inhibitorthickness Baking Classification Kind *6 Blending quantity *7 (μm)temperature (° C.) Comparative 1 10 0.3 140 example Comparative 1 10 0.3140 example Example 1 10 0.3 140 Example 1 10 0.3 140 Example 1 10 0.3140 Example 1 10 0.3 140 Example 1 10 0.3 140 Example 1 10 0.3 140Example 1 10 0.3 140 Example 1 10 0.3 140 Example 1 10 0.3 140 Example 110 0.3 140 Example 1 10 0.3 140 Example 1 10 0.3 140 Example 1 10 0.3140 Example 2 10 0.3 140

TABLE 17 Secondary layer Organic resin Rust inhibitor Solid lubricantCoating Baking Blending Blending Blending thickness temperatureClassification No. Kind *8 quantity *10 Kind *6 quantity *10 Kind *9quantity *10 (μm) (° C.) Comparative 47 1 100 1 20 — — 1.0 140 exampleComparative 48 1 100 1 20 — — 1.0 140 example Example 49 1 100 1 20 — —1.0 140 Example 50 1 100 1 20 — — 1.0 140 Example 51 1 100 1 20 — — 1.0140 Example 52 1 100 1 20 — — 1.0 140 Example 53 1 100 1 20 — — 1.0 140Example 54 1 100 1 20 — — 1.0 140 Example 55 1 100 1 20 — — 1.0 140Example 56 1 100 1 20 — — 1.0 140 Example 57 1 100 1 20 — — 1.0 140Example 58 1 100 1 20 — — 1.0 140 Example 59 1 100 1 20 — — 1.0 140Example 60 1 100 1 20 — — 1.0 140 Example 61 1 100 1 20 — — 1.0 140Example 62 1 100 1 20 — — 1.0 140 Performance Corrosion resistance afterElectrodeposited Classification Corrosion resistance treatmentWeldability paint adhesion Comparative Δ Δ ◯ ⊚ example Comparative X X ⊚⊚ example Example ⊚ ◯+ ⊚ ⊚ Example ◯+ ◯ ⊚ ⊚ Example ◯+ ◯ ⊚ ⊚ Example ◯+◯ ⊚ ⊚ Example ◯ ◯− ⊚ ⊚ Example ◯ ◯− ⊚ ⊚ Example ◯ ◯− ⊚ ⊚ Example ⊚ ◯+ ⊚⊚ Example ⊚ ◯+ ⊚ ⊚ Example ⊚ ◯+ ⊚ ⊚ Example ⊚ ◯+ ⊚ ⊚ Example ⊚ ◯+ ⊚ ⊚Example ⊚ ◯+ ⊚ ⊚ Example ⊚ ◯+ ⊚ ⊚

TABLE 18 Primary layer Phosphoric Water-soluble acid or resin or water-Silane hexafluorometal Water-soluble Plated dispersible resin couplingagent acid phosphate Rust inhibitor steel Blending Blending BlendingBlending Blending Coating Baking Classi- sheet Kind quantity Kindquantity Kind quantity Kind quantity Kind quantity thickness temperaturefication No. *1 *2 *7 *3 *7 *4 *7 *5 *7 *6 *7 (μm) (° C.) Example 63 1 1100 1 25 1 40 1 5 3 10 0.3 140 Example 64 1 1 100 1 25 1 40 1 5 4 10 0.3140 Example 65 1 1 100 1 25 1 40 1 5 5 10 0.3 140 Example 66 1 1 100 125 1 40 1 5 6 10 0.3 140 Example 67 1 1 100 1 25 1 40 1 5 1 10 0.3 140Example 68 1 1 100 1 25 1 40 1 5 1 10 0.3 140 Example 69 1 1 100 1 25 140 1 5 1 10 0.3 140 Example 70 1 1 100 1 25 1 40 1 5 1 10 0.3 140Example 71 1 1 100 1 25 1 40 1 5 1 10 0.3 140 Example 72 1 1 100 1 25 140 1 5 1 10 0.3 140 Example 73 1 1 100 1 25 1 40 1 5 1 10 0.3 140Example 74 1 1 100 1 25 1 40 1 5 1 10 0.3 140 Example 75 1 1 100 1 25 140 1 5 1 10 0.3 140 Example 76 1 1 100 1 25 1 40 1 5 1 10 0.3 140Example 77 1 1 100 1 25 1 40 1 5 1 10 0.3 140 Example 78 1 1 100 1 25 140 1 5 1 10 0.3 140

TABLE 19 Secondary layer Performance Organic resin Rust inhibitor Solidlubricant Coating Corrosion Electro- Blending Blending Blending thick-Baking resistance deposited Classi- Kind quantity Kind quantity Kindquantity ness temperature Corrosion after paint fication No. *8 *10 *6*10 *9 *10 (μm) (° C.) resistance treatment Weldability adhesion Example63 1 100 1 20 — — 1.0 140 ⊚ ◯ ⊚ ⊚ Example 64 1 100 1 20 — — 1.0 140 ⊚ ◯⊚ ⊚ Example 65 1 100 1 20 — — 1.0 140 ⊚ ◯ ⊚ ⊚ Example 66 1 100 1 20 — —1.0 140 ⊚ ◯ ⊚ ⊚ Example 67 1 100 1 20 — — 1.0 140 ⊚ ◯+ ⊚ ⊚ Example 69 2100 1 20 — — 1.0 140 ⊚ ◯+ ⊚ ⊚ Example 70 3 100 1 20 — — 1.0 140 ⊚ ⊚ ⊚ ⊚Example 71 4 100 1 20 — — 1.0 140 ⊚ ◯ ⊚ ⊚ Example 72 5 100 1 20 — — 1.0140 ⊚ ◯ ⊚ ⊚ Example 73 6 100 1 20 — — 1.0 140 ⊚ ◯+ ⊚ ⊚ Example 74 7 1001 20 — — 1.0 140 ⊚ ◯+ ⊚ ⊚ Example 75 8 100 1 20 — — 1.0 140 ⊚ ◯+ ⊚ ⊚Example 76 9 100 1 20 — — 1.0 140 ⊚ ⊚ ⊚ ⊚ Example 77 10 100 1 20 — — 1.0140 ⊚ ◯− ⊚ ⊚ Example 78 11 100 1 20 — — 1.0 140 ⊚ ◯− ⊚ ⊚

TABLE 20 Primary layer Phosphoric Water-soluble acid or Plat- resin orwater- Silane hexafluorometal Water-soluble ed dispersible resincoupling agent acid phosphate Rust inhibitor steel Blending BlendingBlending Blending Blending Coating Baking Classi- sheet Kind quantityKind quantity Kind quantity Kind quantity Kind quantity thicknesstemperature fication No. *1 *2 *7 *3 *7 *4 *7 *5 *7 *6 *7 (μm) (° C.)Example 79 1 1 100 1 25 1 40 1 5 1 10 0.3 140 Comparative 80 1 1 100 125 1 40 1 5 1 10 0.3 140 example Comparative 81 1 1 100 1 25 1 40 1 5 110 0.3 140 example Comparative 82 1 1 100 1 25 1 40 1 5 1 10 0.3 140example Example 83 1 1 100 1 25 1 40 1 5 1 10 0.3 140 Example 84 1 1 1001 25 1 40 1 5 1 10 0.3 140 Example 85 1 1 100 1 25 1 40 1 5 1 10 0.3 140Comparative 86 1 1 100 1 25 1 40 1 5 1 10 0.3 140 example Example 87 1 1100 1 25 1 1 1 5 1 10 0.3 140 Comparative 88 1 1 100 1 25 1 5 1 5 1 100.3 140 example Comparative 89 1 1 100 1 25 1 20 1 5 1 10 0.3 140example Comparative 90 1 1 100 1 25 1 40 1 5 1 10 0.3 140 exampleExample 91 1 1 100 1 25 1 100 1 5 1 10 0.3 140

TABLE 21 Secondary layer Performance Organic resin Rust inhibitor Solidlubricant Coating Corrosion Electro- Blending Blending Blending thick-Baking resistance deposited Classi- Kind quantity Kind quantity Kindquantity ness temperature Corrosion after paint fication No. *8 *10 *6*10 *9 *10 (μm) (° C.) resistance treatment Weldability adhesion Example79 12 100 1 20 — — 1.0 140 ⊚ ◯ ⊚ ⊚ Com- 80 13 100 1 20 — — 1.0 140 ◯ X ⊚⊚ parative example Com- 81 14 100 1 20 — — 1.0 140 ◯ X ⊚ ⊚ parativeexample Com- 82 15 100 1 20 — — 1.0 140 ◯ X ⊚ ⊚ parative example Example83 16 100 1 20 — — 1.0 140 ⊚ ⊚ ⊚ ⊚ Example 84 17 100 1 20 — — 1.0 140 ⊚⊚ ⊚ ⊚ Example 85 18 100 1 20 — — 1.0 140 ⊚ ⊚ ⊚ ⊚ Com- 86 19 100 1 20 — —1.0 140 ◯ Δ ⊚ ⊚ parative example Example 87 20 100 1 20 — — 1.0 140 ⊚ ◯+⊚ ⊚ Com- 88 21 100 1 20 — — 1.0 140 Δ X ⊚ ⊚ parative example Com- 89 22100 1 20 — — 1.0 140 Δ Δ ⊚ ⊚ parative example Com- 90 23 100 1 20 — —1.0 140 Δ Δ ⊚ ⊚ parative example Example 91 1 100 2 20 — — 1.0 140 ⊚ ◯ ⊚⊚

TABLE 22 Primary layer Phosphoric Water-soluble acid or resin or water-Silane hexafluorometal Water-soluble Plated dispersible resin couplingagent acid phosphate Rust inhibitor steel Blending Blending BlendingBlending Blending Coating Baking Classi- sheet Kind quantity Kindquantity Kind quantity Kind quantity Kind quantity thickness temperaturefication No. *1 *2 *7 *3 *7 *4 *7 *5 *7 *6 *7 (μm) (° C.) Example 92 1 1100 1 25 1 40 1 5 1 10 0.3 140 Example 93 1 1 100 1 25 1 40 1 5 1 10 0.3140 Example 94 1 1 100 1 25 1 40 1 5 1 10 0.3 140 Example 95 1 1 100 125 1 40 1 5 1 10 0.3 140 Example 96 1 1 100 1 25 1 40 1 5 1 10 0.3 140Example 97 1 1 100 1 25 1 40 1 5 1 10 0.3 140 Example 98 1 1 100 1 25 140 1 5 1 10 0.3 140 Example 99 1 1 100 1 25 1 40 1 5 1 10 0.3 140Example 100 1 1 100 1 25 1 40 1 5 1 10 0.3 140 Example 101 1 1 100 1 251 40 1 5 1 10 0.3 140 Example 102 1 1 100 1 25 1 40 1 5 1 10 0.3 140Example 103 1 1 100 1 25 1 40 1 5 1 10 0.3 140

TABLE 23 Secondary layer Performance Organic resin Rust inhibitor Solidlubricant Coating Corrosion Electro- Blending Blending Blending thick-Baking resistance deposited Classi- Kind quantity Kind quantity Kindquantity ness temperature Corrosion after paint fication No. *8 *10 *6*10 *9 *10 (μm) (° C.) resistance treatment Weldability adhesion Example92 1 100 3 20 — — 1.0 140 ⊚ ◯ ⊚ ⊚ Example 93 1 100 4 20 — — 1.0 140 ⊚ ◯⊚ ⊚ Example 94 1 100 5 20 — — 1.0 140 ⊚ ◯ ⊚ ⊚ Example 95 1 100 6 20 — —1.0 140 ◯ ◯− ⊚ ⊚ Example 96 1 100 1 + 4 10 + 10 — — 1.0 140 ⊚ ◯+ ⊚ ⊚Example 97 1 100 1 + 5 20 + 10 — — 1.0 140 ⊚ ◯+ ⊚ ⊚ Example 98 1 100 1 +6 20 + 10 — — 1.0 140 ⊚ ◯+ ⊚ ⊚ Example 99 1 100 1 + 10 + 7 + 3 — — 1.0140 ⊚ ◯+ ⊚ ⊚ 4 + 6 Example 100 1 100 1 + 10 + 7 + 3 — — 1.0 140 ⊚ ◯+ ⊚ ⊚5 + 6 Example 101 1 100 4 + 9 + 8 + 3 — — 1.0 140 ⊚ ◯+ ⊚ ⊚ 5 + 6 Example102 1 100 — — — — 1.0 140 ◯ ◯− ⊚ ⊚ Example 103 1 100 1  1 — — 1.0 140 ◯◯− ⊚ ⊚

TABLE 24 Primary layer Phosphoric Water-soluble acid or Plat- resin orwater- Silane hexafluorometal Water-soluble ed dispersible resincoupling agent acid phosphate Rust inhibitor steel Blending BlendingBlending Blending Blending Coating Baking Classi- sheet Kind quantityKind quantity Kind quantity Kind quantity Kind quantity thicknesstemperature fication No. *1 *2 *7 *3 *7 *4 *7 *5 *7 *6 *7 (μm) (° C.)Example 104 1 1 100 1 25 1 40 1 5 1 10 0.3 140 Example 105 1 1 100 1 251 40 1 5 1 10 0.3 140 Example 106 1 1 100 1 25 1 40 1 5 1 10 0.3 140Example 107 1 1 100 1 25 1 40 1 5 1 10 0.3 140 Example 108 1 1 100 1 251 40 1 5 1 10 0.3 140 Comparative 109 1 1 100 1 25 1 40 1 5 1 10 0.3 140example Comparative 110 1 1 100 1 25 1 40 1 5 1 10 0.3 140 exampleExample 111 1 1 100 1 25 1 40 1 5 1 10 0.3 140 Example 112 1 1 100 1 251 40 1 5 1 10 0.3 140 Comparative 113 1 1 100 1 25 1 40 1 5 1 10 0.3 140example Comparative 114 1 1 100 1 25 1 40 1 5 1 10 0.3 140 exampleExample 115 1 1 100 1 25 1 40 1 5 1 10 0.3 140 Example 116 1 1 100 1 251 40 1 5 1 10 0.3 140 Example 117 1 1 100 1 25 1 40 1 5 — — 0.3 140

TABLE 25 Secondary layer Performance Organic resin Rust inhibitor Solidlubricant Coating Corrosion Electro- Blending Blending Blending thick-Baking resistance deposited Classi- Kind quantity Kind quantity Kindquantity ness temperature Corrosion after paint fication No. *8 *10 *6*10 *9 *10 (μm) (° C.) resistance treatment Weldability adhesion Example104 1 100 1 50 — — 1.0 140 ⊚ ◯ ◯ ⊚ Example 105 1 100 1 30 — — 1.0 140 ⊚◯+ ◯ ⊚ Example 106 1 100 1 20 1 5 1.0 140 ⊚ ⊚ ⊚ ⊚ Example 107 1 100 1 202 5 1.0 140 ⊚ ⊚ ⊚ ⊚ Example 108 1 100 1 20 3 5 1.0 140 ⊚ ⊚ ⊚ ⊚ Com- 109— — — — — — — — X X ⊚ ⊚ parative example Com- 110 1 100 1 20 1 5 0.1 140Δ Δ ◯ ⊚ parative example Example 111 1 100 1 20 1 5 0.3 140 ◯ ◯ ◯ ⊚Example 112 1 100 1 20 1 5 2.0 140 ⊚ ⊚ ◯ ◯ Com- 113 1 100 1 20 1 5 3.0140 ⊚ ◯ X X parative example Com- 114 1 100 1 20 1 5 7.0 140 ⊚ X ◯ ◯parative ※ example Example 115 1 100 1 20 2 5 1.0 110 ⊚ ◯+ ⊚ ⊚ Example116 1 100 1 20 2 5 1.0 200 ◯ ◯ ⊚ ⊚ Example 117 1 100 1 20 2 5 1.0 140 ⊚⊚ ⊚ ⊚ ※ As the conductive agent, 80 parts by mass of iron phosphide isadded to 100 parts by mass of the solid matter in the resin composition.

EXAMPLE 2

The surface treatment coating compositions for forming the primarycoating were prepared using the respective resin compositions ofwater-soluble or water-dispersible epoxy resins shown in Table 26 orusing the respective water dispersed polyurethane resines shown in Table27, adding appropriately the respective silane coupling agents (Table3), the phosphoric acid or hexafluorometal acids (Table 4), thewater-soluble phosphates (Table 5), and non-chromium based rustinhibitors (Table 6), which were used in [Example 1]. The pH of themixture was agitated to a range from 0.5 to 6 using ammonia water,nitric acid, acetic acid, sulfuric acid, phosphoric acid,hexafluorometal acid, and the like. Then, the mixture was agitated usinga disperser for coating (sand-grinder) for a specified time to preparethe respective surface treatment coating compositions.

The water-soluble or water-dispersible epoxy resins shown in Table 26were prepared by the following procedure.

MANUFACTURE EXAMPLE 1

To a four-neck flask equipped with a thermometer, an agitator, and acooling tube, 787.4 g of Epicoat 1007 (an epoxy resin having epoxyequivalent of 2000; manufactured by Shell Japan Ltd.), and 425 g ofpropyleneglycol monobutylether were added. The mixture was agitated at110° C. to bring the mixture homogeneous and transparent. Then, themixture was cooled to 100° C. After that, 20.7 g of diethanolamine wasadded to the mixture to conduct reaction for 1 hour. The epoxy aminevalue of the reacted mixture was determined to confirm that the observedvalue agreed with the theoretical value. Then, 16.5 g of3-amino-1,2,4-tolyazole (molecular weight of 84) was added to themixture to conduct reaction for 5 hours. After that, 250 g ofpropyleneglycol monobutylether was added to the mixture to obtain themodified epoxy resin (D1). A 23.3 g of phosphoric acid was added to the(D1) modified epoxy resin, and water was dropped thereto to mix themtogether, thus obtained the water-epoxy resin dispersion (E1) with solidmatter content of 20%.

MANUFACTURE EXAMPLE 2

To a four-neck flask equipped with a thermometer, an agitator, and acooling tube, 546 g of Epicoat 1004 (an epoxy resin having epoxyequivalent of 925; manufactured by Shell Japan Ltd.), and 311 g ofpropyleneglycol monobutylether were added. The mixture was agitated at110° C. to bring the mixture homogeneous and transparent. Then, themixture was cooled to 100° C. After that, 31.5 g of diethanolamine wasadded to the mixture to conduct reaction for 1 hour. The epoxy aminevalue of the reacted mixture was determined to confirm that the observedvalue agreed with the theoretical value. Then, 25.2 g of3-amino-1,2,4-tolyazole (molecular weight of 84) was added to themixture to conduct reaction for 5 hours. After that, 182.6 g ofpropyleneglycol monobutylether was added to the mixture to obtain themodified epoxy resin (D2). A 35.3 g of phosphoric acid was added to the(D2) modified epoxy resin, and water was dropped thereto to mix themtogether, thus obtained the water-epoxy resin dispersion (E2) with solidmatter content of 20%.

MANUFACTURE EXAMPLE 3

The reaction similar with that in Manufacture Example 1 was conductedexcept for changing the quantity of diethanolamine to 12.4 g, and thequantity of 3-amino-1,2,4-tolyazole to 23.1 g, thus obtained themodified epoxy resin. The modified epoxy resin was mixed with water toobtain the water-epoxy resin dispersion (E3) with solid matter contentof 20%.

MANUFACTURE EXAMPLE 4 COMPARATIVE EXAMPLE

To a four-neck flask equipped with a thermometer, an agitator, and acooling tube, 186.6 g of Epicoat 1001 (an epoxy resin having epoxyequivalent of about 475 and number average molecular weight of about900; manufactured by Japan Epoxy Resins Co., Ltd.), and 115.2 g ofpropyleneglycol monobytutylether were charged. The mixture was heated to110° C. to agitate to establish a homogeneous and transparent state. Themixture was cooled to 100° C. Then, 25.5 g of diethanolamine was addedto the mixture to hold at 100° C. for 1 hour. After that, 68.0 g ofpropyleneglycol monobutylether was added to the mixture to obtain themodified epoxy resin solution (D4). A 23.3 g of phosphoric acid wasadded to the (D4) modified epoxy resin solution, and water was droppedinto the solution to mix them together, thus obtained the water-epoxyresin dispersion (E4) with solid matter content of 20%.

MANUFACTURE EXAMPLE 5 COMPARATIVE EXAMPLE

The reaction similar with that in Manufacture Example 1 was conductedexcept for changing 16.5 g of 3-amino-1,2,4-tolyazole to 14.7 g ofN-methyl-ethanolamine, thus obtained the modified epoxy resin (D5). The(D5) modified epoxy resin was mixed with water to obtain the water-epoxyresin dispersion (E5)with solid matter content of 20%.

The surface treatment coating compositions for forming the secondarycoating were prepared using the respective resin compositions shown inTable 7 and Table 8 similar with the case of [Example 1], addingappropriately the respective non-chromium based rust inhibitors (Table6) and solid lubricants (Table 9) silane coupling agents (Table 3) usedin [Example 1]. The mixture was agitated using a disperser for coating(sand-grinder) for a specified time to prepare the surface treatmentcoating composition. The method for synthesizing the base resins(reaction products) of the resin composition given in Table 7 and Table8 was the same as that described in [Example 1].

As the treating base sheets, the plated steel sheets given in Table 1,which are the plated steel sheets with cold-rolled steel sheets as thebase sheets were adopted. The plated steel sheets are for householdelectric appliances, building materials, and automobile parts. Thethickness of the steel sheets was selected responding to the objectivesof evaluations. After alkali degreasing, washing with water, and dryingon the surface of the plated steel sheets, the above-describedrespective surface treatment coating compositions for forming theprimary coating were applied using a roll coater, and then thecompositions were heated to dry at various temperatures. The coatingthickness was adjusted by the solid matter content (heating residue) ofthe surface treatment coating composition or by the applicationconditions (roll pressing force, rotational speed, and the like).

Then, the respective coating compositions for forming the secondarycoating were applied using a roll coater, and were heated to dry atvarious temperatures. The coating thickness was adjusted by the solidmatter content (heating residue) of the surface treatment coatingcomposition or by the application conditions (roll pressing force,rotational speed, and the like)

Tables 28 through 43 show the result of evaluation of thus preparedsurface-treated steel sheets in terms of coating composition and qualityperformance (corrosion resistance, corrosion resistance after forming,weldability, and electrodeposited paint adhesion). The evaluation ofquality was given in the following procedure.

(1) Corrosion Resistance

Each sample was degreased by FC-4460 (manufactured by Japan ParkerizingCo., Ltd.) under the condition of 60° C. for 2 minutes. Then, the samplewas subjected to the following-given combined cycle test (CCT) toevaluate the corrosion resistance based on the are a percentage of whiterust generation and the area percentage of red rust generation after 50cycles.

The evaluation criterion is the following.

-   ⊚: less than 5% of the area percentage of white rust generation-   ◯+: 5% or more and less than 10% of the area percentage of white    rust generation-   ◯: 10% or more and less than 30% of the area percentage of white    rust generation-   ◯−: 30% or more of the area percentage of white rust generation,    without red rust generation-   Δ: with red rust generation, less than 10% of area percentage of red    rust generation-   X: 10% or more of area percentage of red rust generation    (2) Corrosion Resistance After Forming

Each sample was subjected to deformation and sliding with a draw-beadunder the condition given below. Thus treated sample was degreased byFC-4460 (manufactured by Japan Parkerizing Co., Ltd.) under thecondition of 60° C. for 2 minutes. Then, the sample was treated by CCTgiven in the “(1) Corrosion resistance” to evaluate the corrosionresistance after forming based on the area percentage of white rustgeneration and the area percentage of red rust generation after 36cycles.

-   Pressing load: 800 kgf-   Draw-out speed: 1000 mm/min-   Bead shoulder R: 2 mm on male side, 3 mm on female side-   Penetration depth: 7 mm-   Oil: Pleton R-352L; manufactured by Sugimura Chemical Industry, Co.,    Ltd.    The evaluation criterion is the following.-   ⊚: less than 5% of the area percentage of white rust generation-   ◯+: 5% or more and less than 10% of the area percentage of white    rust generation-   ◯: 10% or more and less than 30% of the area percentage of white    rust generation-   ◯−: 30% or more of the area percentage of white rust generation,    without red rust generation-   Δ: with red rust generation, less than 10% of area percentage of red    rust generation-   X: 10% or more of area percentage of red rust generation    (3) Weldability

The weldability was evaluated under the same test condition and with thesame evaluation criterion with those of [Example 1].

(4) Electrodeposited Paint Adhesion

The electrodeposited paint adhesion was evaluated under the same testcondition and with the same evaluation criterion with those of [Example1].

TABLE 26 No. Water-epoxy resin dispersion 1 E1 of (ManufactureExample 1) given in the description 2 E2 of (Manufacture Example 2)given in the description 3 E3 of (Manufacture Example 3) given in thedescription 4 E4 of (Manufacture Example 4) given in the description 5E5 of (Manufacture Example 5) given in the description

TABLE 27 No. Water dispersed polyurethane resine (Product name) Ionicity1 UCoat UX-2505, manufactured by Sanyo Chemical Nonion Industries, Ltd.2 Superflex E2500, manufactured by Dai-ichi Kogyo Nonion Seiyaku Co.,Ltd. 3 Adekabontighter UX206, manufactured by Asahi Nonion Denka KogyoK.K. 4 Takerac W-635, manufactured by Mitsui Takeda Nonion Chemicals,Inc. 5 Superflex 600, manufactured by Dai-ichi Kogyo Cation Seiyaku Co.,Ltd. 6 Permarin UC-20, manufactured by Sanyo Chemical Cation Industries,Ltd.Symbols *1 through *10 found in Tables 28 through 43 designate thefollowing, respectively.

-   *1: No. given in Table 1, (plated steel sheet)-   *2: No. given in Table 26, (water-soluble or water-dispersible epoxy    resin)-   *3: No. given in Table 27, (water dispered polyurethane resin)-   *4: No. given in Table 3, (silane coupling agent)-   *5: No. given in Table 4, (phosphoric acid or hexafluorometal acid)-   *6: No. given in Table 5, (water-soluble phosphate)-   *7: No. given in Table 6, (rust inhibitor)-   *8: Parts by mass, (for the ingredients other than water-soluble or    water-dispersible epoxy resin, parts by mass to 100 parts by mass of    the solid matter in the water-soluble or water-dispersible epoxy    resin)-   *9: No. given in Table 7 and 8, (resin composition)-   *10: No. given in Table 9, (solid lubricant)-   *11: Parts by mass (for the ingredients other than organic resin,    parts by mass to 100 parts by mass of the solid matter in the    organic resin)

TABLE 28 Primary layer Water-soluble resin or Water Phosphoric water-dispersed acid or hexa- dispersible polyurethane Silane couplingfluorometal Water-soluble resin resine agent acid phosphate Rustinhibitor Plated Blend- Blend- Blend- Blend- Blend- Blend- CoatingBaking steel ing ing ing ing ing ing thick- tem- Classi- sheet Kindquantity Kind quantity Kind quantity Kind quantity Kind quantity Kindquantity ness perature fication No. *1 *2 *8 *3 *8 *4 *8 *5 *8 *6 *8 *7*8 (μm) (° C.) Comparative 1 1 — 50 — — 1 25 1 40 — — — — 0.3 140example Comparative 2 1 1 50 1 50 — — 1 40 — — — — 0.3 140 exampleExample 3 1 1 50 1 50 1 5 1 40 — — — — 0.3 140 Example 4 1 1 50 1 50 115 1 40 — — — — 0.3 140 Example 5 1 1 50 1 50 1 50 1 40 — — — — 0.3 140Example 6 1 1 50 1 50 1 100 1 40 — — — — 0.3 140 Comparative 7 1 1 50 150 1 500 1 40 — — — — 0.3 140 example Comparative 8 1 1 50 1 50 1 25 — —— — — — 0.3 140 example Example 9 1 1 50 1 50 1 25 1 1 — — — — 0.3 140Example 10 1 1 50 1 50 1 25 1 5 — — — — 0.3 140 Example 11 1 1 50 1 50 125 1 20 — — — — 0.3 140 Example 12 1 1 50 1 50 1 25 1 40 — — — — 0.3 140Comparative 13 1 1 50 1 50 1 25 1 100 — — — — 0.3 140 exampleComparative 14 1 1 100  — — 1 25 1 40 — — — — 0.3 140 example Example 151 1 90 1 10 1 25 1 40 — — — — 0.3 140 Example 16 1 1 70 1 30 1 25 1 40 —— — — 0.3 140 Example 17 1 1 30 1 70 1 25 1 40 — — — — 0.3 140 Example18 1 1 10 1 90 1 25 1 40 — — — — 0.3 140 Comparative 19 1 — — 1 100  125 1 40 — — — — 0.3 140 example

TABLE 29 Secondary layer Performance Organic resin Rust inhibitor Solidlubricant Coating Corrosion Electro- Blending Blending Blending thick-Baking resistance deposited Classi- Kind quantity Kind quantity Kindquantity ness temperature Corrosion after paint fication No. *9 *11 *7*11 *10 *11 (μm) (° C.) resistance treatment Weldability adhesion Com- 11 100 1 20 — — 1.0 140 X X ⊚ ⊚ parative example Com- 2 1 100 1 20 — —1.0 140 Δ X ⊚ ⊚ parative example Example 3 1 100 1 20 — — 1.0 140 ◯ ◯ ⊚⊚ Example 4 1 100 1 20 — — 1.0 140 ◯ ◯ ⊚ ⊚ Example 5 1 100 1 20 — — 1.0140 ◯ ◯ ⊚ ⊚ Example 6 1 100 1 20 — — 1.0 140 ◯ ◯ ⊚ ⊚ Com- 7 1 100 1 20 —— 1.0 140 Δ X ◯ ◯ parative example Com- 8 1 100 1 20 — — 1.0 140 X X ⊚ ⊚parative example Example 9 1 100 1 20 — — 1.0 140 ◯ ◯ ⊚ ⊚ Example 10 1100 1 20 — — 1.0 140 ◯ ◯ ⊚ ⊚ Example 11 1 100 1 20 — — 1.0 140 ◯ ◯ ⊚ ⊚Example 12 1 100 1 20 — — 1.0 140 ◯ ◯ ⊚ ⊚ Com- 13 1 100 1 20 — — 1.0 140Δ X ⊚ ⊚ parative example Com- 14 1 100 1 20 — — 1.0 140 ◯ Δ ⊚ ⊚ parativeexample Example 15 1 100 1 20 — — 1.0 140 ◯ ◯ ⊚ ⊚ Example 16 1 100 1 20— — 1.0 140 ◯ ◯ ⊚ ⊚ Example 17 1 100 1 20 — — 1.0 140 ◯ ◯ ⊚ ⊚ Example 181 100 1 20 — — 1.0 140 ◯ ◯ ⊚ ⊚ Com- 19 1 100 1 20 — — 1.0 140 Δ Δ ⊚ ⊚parative example

TABLE 30 Primary layer Water-soluble resin or water- Water dispersedSilane coupling Phosphoric acid or Plated dispersible resin polyurethaneresine agent hexafluorometal acid steel Blending Blending BlendingBlending Classification No. sheet *1 Kind *2 quantity *8 Kind *3quantity *8 Kind *4 quantity *8 Kind *5 quantity *8 Example 20 1 1 50 150 1 25 1 40 Example 21 1 1 50 1 50 1 25 1 40 Example 22 1 1 50 1 50 125 1 40 Example 23 1 1 50 1 50 1 25 1 40 Comparative 24 1 1 50 1 50 1 251 40 example Example 25 1 1 50 1 50 1 25 1 40 Example 26 1 1 50 1 50 125 1 40 Example 27 1 1 50 1 50 1 25 1 40 Example 28 1 1 50 1 50 1 25 140 Example 29 1 1 50 1 50 1 25 1 40 Example 30 1 1 50 1 50 1 25 1 40Example 31 1 1 50 1 50 1 25 1 40 Example 32 1 1 50 1 50 1 25 1 40Comparative 33 1 1 50 1 50 1 25 1 40 example Example 34 1 1 50 1 50 1 251 40 Example 35 1 1 50 1 50 1 25 1 40 Example 36 1 1 50 1 50 1 25 1 40Example 37 1 1 50 1 50 1 25 1 40 Primary layer Water-soluble phosphateRust inhibitor Coating Baking Blending Blending thickness temperatureClassification No. Kind *6 quantity *8 Kind *7 quantity *8 (μm) (° C.)Example 20 1 0.5 — — 0.3 140 Example 21 1 5 — — 0.3 140 Example 22 1 10— — 0.3 140 Example 23 1 30 — — 0.3 140 Comparative 24 1 80 — — 0.3 140example Example 25 — — 1 0.5 0.3 140 Example 26 — — 1 10 0.3 140 Example27 — — 1 30 0.3 140 Example 28 — — 1 70 0.3 140 Example 29 1 5 1 0.5 0.3140 Example 30 1 5 1 10 0.3 140 Example 31 1 10 1 10 0.3 140 Example 321 10 1 30 0.3 140 Comparative 33 1 5 1 10 0.005 140 example Example 34 15 1 10 0.01 140 Example 35 1 5 1 10 0.1 140 Example 36 1 5 1 10 0.6 140Example 37 1 5 1 10 1.0 140

TABLE 31 Secondary layer Organic resin Rust inhibitor Solid lubricantCoating Baking Kind Blending Kind Blending Kind Blending thicknesstemperature Classification No. *9 quantity *11 *7 quantity *11 *10quantity *11 (μm) (° C.) Example 20 1 100 1 20 — — 1.0 140 Example 21 1100 1 20 — — 1.0 140 Example 22 1 100 1 20 — — 1.0 140 Example 23 1 1001 20 — — 1.0 140 Comparative 24 1 100 1 20 — — 1.0 140 example Example25 1 100 1 20 — — 1.0 140 Example 26 1 100 1 20 — — 1.0 140 Example 27 1100 1 20 — — 1.0 140 Example 28 1 100 1 20 — — 1.0 140 Example 29 1 1001 20 — — 1.0 140 Example 30 1 100 1 20 — — 1.0 140 Example 31 1 100 1 20— — 1.0 140 Example 32 1 100 1 20 — — 1.0 140 Comparative 33 1 100 1 20— — 1.0 140 example Example 34 1 100 1 20 — — 1.0 140 Example 35 1 100 120 — — 1.0 140 Example 36 1 100 1 20 — — 1.0 140 Example 37 1 100 1 20 —— 1.0 140 Performance Corrosion resistance Corrosion afterElectrodeposited Classification No. resistance treatment Weldabilitypaint adhesion Example 20 ◯ ◯ ⊚ ⊚ Example 21 ◯ ◯ ⊚ ⊚ Example 22 ◯ ◯ ⊚ ⊚Example 23 ◯ ◯ ⊚ ⊚ Comparative 24 Δ Δ ⊚ ⊚ example Example 25 ◯+ ◯+ ⊚ ⊚Example 26 ◯+ ◯+ ⊚ ⊚ Example 27 ◯+ ◯+ ◯ ⊚ Example 28 ◯ ◯ ◯ ⊚ Example 29◯+ ◯ ⊚ ⊚ Example 30 ⊚ ◯ ⊚ ⊚ Example 31 ⊚ ◯+ ◯ ⊚ Example 32 ⊚ ◯+ ◯ ⊚Comparative 33 X X ⊚ ⊚ example Example 34 ◯− ◯ ⊚ ⊚ Example 35 ◯ ◯ ⊚ ⊚Example 36 ◯+ ◯ ◯ ◯ Example 37 ◯+ ◯+ ◯ ◯

TABLE 32 Primary layer Water-soluble resin or water- Water dispersedSilane coupling Phosphoric acid or Plated dispersible resin polyurethaneresine agent hexafluorometal acid steel Blending Blending BlendingBlending Classification No. sheet *1 Kind *2 quantity *8 Kind *3quantity *8 Kind *4 quantity *8 Kind *5 quantity *8 Comparative 38 1 150 1 50 1 25 1 40 example Comparative 39 1 1 50 1 50 1 25 1 40 exampleExample 40 1 1 50 1 50 1 25 1 40 Example 41 1 1 50 1 50 1 25 1 40Example 42 1 1 50 1 50 1 25 1 40 Example 43 2 1 50 1 50 1 25 1 40Example 44 3 1 50 1 50 1 25 1 40 Example 45 4 1 50 1 50 1 25 1 40Example 46 5 1 50 1 50 1 25 1 40 Example 47 6 1 50 1 50 1 25 1 40Example 48 7 1 50 1 50 1 25 1 40 Example 49 8 1 50 1 50 1 25 1 40Example 50 9 1 50 1 50 1 25 1 40 Example 51 1 2 50 1 50 1 25 1 40Example 52 1 3 50 1 50 1 25 1 40 Primary layer Water-soluble phosphateRust inhibitor Coating Baking Blending Blending thickness temperatureClassification No. Kind *6 quantity *8 Kind *7 quantity *8 (μm) (° C.)Comparative 38 1 5 1 10 1.5 140 example Comparative 39 1 5 1 10 0.3 25example Example 40 1 5 1 10 0.3 50 Example 41 1 5 1 10 0.3 100 Example42 1 5 1 10 0.3 200 Example 43 1 5 1 10 0.3 140 Example 44 1 5 1 10 0.3140 Example 45 1 5 1 10 0.3 140 Example 46 1 5 1 10 0.3 140 Example 47 15 1 10 0.3 140 Example 48 1 5 1 10 0.3 140 Example 49 1 5 1 10 0.3 140Example 50 1 5 1 10 0.3 140 Example 51 1 5 1 10 0.3 140 Example 52 1 5 110 0.3 140

TABLE 33 Secondary layer Organic resin Rust inhibitor Solid lubricantCoating Baking Kind Blending Kind Blending Kind Blending thicknesstemperature Classification No. *9 quantity *11 *7 quantity *11 *10quantity *11 (μm) (° C.) Comparative 38 1 100 1 20 — — 1.0 140 exampleComparative 39 1 100 1 20 — — 1.0 140 example Example 40 1 100 1 20 — —1.0 140 Example 41 1 100 1 20 — — 1.0 140 Example 42 1 100 1 20 — — 1.0140 Example 43 1 100 1 20 — — 1.0 140 Example 44 1 100 1 20 — — 1.0 140Example 45 1 100 1 20 — — 1.0 140 Example 46 1 100 1 20 — — 1.0 140Example 47 1 100 1 20 — — 1.0 140 Example 48 1 100 1 20 — — 1.0 140Example 49 1 100 1 20 — — 1.0 140 Example 50 1 100 1 20 — — 1.0 140Example 51 1 100 1 20 — — 1.0 140 Example 52 1 100 1 20 — — 1.0 140Performance Corrosion resistance Corrosion after ElectrodepositedClassification No. resistance treatment Weldability paint adhesionComparative 38 ⊚ ⊚ X X example Comparative 39 Δ Δ ⊚ ⊚ example Example 40◯− ◯ ⊚ ⊚ Example 41 ◯ ◯ ⊚ ⊚ Example 42 ◯− ◯ ⊚ ⊚ Example 43 ◯+ ◯+ ◯ ⊚Example 44 ◯ ◯ ⊚ ⊚ Example 45 ⊚ ◯ ◯ ◯ Example 46 ⊚ ◯+ ◯ ◯ Example 47 ⊚ ⊚◯ ◯ Example 48 ◯+ ◯+ ◯ ◯ Example 49 ⊚ ◯+ ◯ ◯ Example 50 ⊚ ◯+ ◯ ◯ Example51 ⊚ ⊚ ◯ ◯ Example 52 ⊚ ⊚ ◯ ◯

TABLE 34 Primary layer Water-soluble resin or water- Water dispersedSilane coupling Phosphoric acid or Plated dispersible resin polyurethaneresine agent hexafluorometal acid steel Blending Blending BlendingBlending Classification No. sheet *1 Kind *2 quantity *8 Kind *3quantity *8 Kind *4 quantity *8 Kind *5 quantity *8 Comparative 53 1 450 1 50 1 25 1 40 example Comparative 54 1 5 50 1 50 1 25 1 40 exampleExample 55 1 1 50 1 50 2 25 1 40 Example 56 1 1 50 1 50 3 25 1 40Example 57 1 1 50 1 50 4 25 1 40 Example 58 1 1 50 1 50 5 25 1 40Example 59 1 1 50 1 50 6 25 1 40 Example 60 1 1 50 1 50 7 25 1 40Example 61 1 1 50 1 50 8 25 1 40 Example 62 1 1 50 1 50 1 25 2 40Example 63 1 1 50 1 50 1 25 3 40 Example 64 1 1 50 1 50 1 25 4 40Example 65 1 1 50 1 50 1 25 1 40 Example 66 1 1 50 1 50 1 25 1 40Example 67 1 1 50 1 50 1 25 1 40 Example 68 1 1 50 1 50 1 25 1 40Primary layer Water-soluble phosphate Rust inhibitor Coating BakingBlending Blending thickness temperature Classification No. Kind *6quantity *8 Kind *7 quantity *8 (μm) (° C.) Comparative 53 1 5 1 10 0.3140 example Comparative 54 1 5 1 10 0.3 140 example Example 55 1 5 1 100.3 140 Example 56 1 5 1 10 0.3 140 Example 57 1 5 1 10 0.3 140 Example58 1 5 1 10 0.3 140 Example 59 1 5 1 10 0.3 140 Example 60 1 5 1 10 0.3140 Example 61 1 5 1 10 0.3 140 Example 62 1 5 1 10 0.3 140 Example 63 15 1 10 0.3 140 Example 64 1 5 1 10 0.3 140 Example 65 2 5 1 10 0.3 140Example 66 3 5 1 10 0.3 140 Example 67 4 5 1 10 0.3 140 Example 68 1 5 210 0.3 140

TABLE 35 Secondary layer Organic resin Rust inhibitor Solid lubricantCoating Baking Kind Blending Kind Blending Kind Blending thicknesstemperature Classification No. *9 quantity *11 *7 quantity *11 *10quantity *11 (μm) (° C.) Comparative 53 1 100 1 20 — — 1.0 140 exampleComparative 54 1 100 1 20 — — 1.0 140 example Example 55 1 100 1 20 — —1.0 140 Example 56 1 100 1 20 — — 1.0 140 Example 57 1 100 1 20 — — 1.0140 Example 58 1 100 1 20 — — 1.0 140 Example 59 1 100 1 20 — — 1.0 140Example 60 1 100 1 20 — — 1.0 140 Example 61 1 100 1 20 — — 1.0 140Example 62 1 100 1 20 — — 1.0 140 Example 63 1 100 1 20 — — 1.0 140Example 64 1 100 1 20 — — 1.0 140 Example 65 1 100 1 20 — — 1.0 140Example 66 1 100 1 20 — — 1.0 140 Example 67 1 100 1 20 — — 1.0 140Example 68 1 100 1 20 — — 1.0 140 Performance Corrosion resistanceCorrosion after Electrodeposited Classification No. resistance treatmentWeldability paint adhesion Comparative 53 Δ Δ ◯ ⊚ example Comparative 54X X ⊚ ⊚ example Example 55 ⊚ ◯+ ⊚ ⊚ Example 56 ◯+ ◯+ ⊚ ⊚ Example 57 ◯+◯+ ⊚ ⊚ Example 58 ◯+ ◯+ ⊚ ⊚ Example 59 ◯ ◯ ⊚ ⊚ Example 60 ◯ ◯ ⊚ ⊚Example 61 ◯ ◯ ⊚ ⊚ Example 62 ⊚ ◯+ ⊚ ⊚ Example 63 ⊚ ◯+ ⊚ ⊚ Example 64 ⊚◯+ ⊚ ⊚ Example 65 ⊚ ◯+ ⊚ ⊚ Example 66 ⊚ ◯+ ⊚ ⊚ Example 67 ⊚ ◯+ ⊚ ⊚Example 68 ⊚ ◯+ ⊚ ⊚

TABLE 36 Primary layer Water-soluble resin or water- Water dispersedSilane coupling Phosphoric acid or Plated dispersible resin polyurethaneresine agent hexafluorometal acid steel Blending Blending BlendingBlending Classification No. sheet *1 Kind *2 quantity *8 Kind *3quantity *8 Kind *4 quantity *8 Kind *5 quantity *8 Example 69 1 1 50 150 1 25 1 40 Example 70 1 1 50 1 50 1 25 1 40 Example 71 1 1 50 1 50 125 1 40 Example 72 1 1 50 1 50 1 25 1 40 Example 73 1 1 50 1 50 1 25 140 Example 74 1 1 50 2 50 1 25 1 40 Example 75 1 1 50 3 50 1 25 1 40Example 76 1 1 50 4 50 1 25 1 40 Example 77 1 1 50 5 50 1 25 1 40Example 78 1 1 50 6 50 1 25 1 40 Example 79 1 1 50 1 50 1 25 1 40Example 80 1 1 50 1 50 1 25 1 40 Example 81 1 1 50 1 50 1 25 1 40Example 82 1 1 50 1 50 1 25 1 40 Example 83 1 1 50 1 50 1 25 1 40Example 84 1 1 50 1 50 1 25 1 40 Example 85 1 1 50 1 50 1 25 1 40Primary layer Water-soluble phosphate Rust inhibitor Coating BakingBlending Blending thickness temperature Classification No. Kind *6quantity *8 Kind *7 quantity *8 (μm) (° C.) Example 69 1 5 3 10 0.3 140Example 70 1 5 4 10 0.3 140 Example 71 1 5 5 10 0.3 140 Example 72 1 5 610 0.3 140 Example 73 1 5 7 10 0.3 140 Example 74 1 5 1 10 0.3 140Example 75 1 5 1 10 0.3 140 Example 76 1 5 1 10 0.3 140 Example 77 1 5 110 0.3 140 Example 78 1 5 1 10 0.3 140 Example 79 1 5 1 10 0.3 140Example 80 1 5 1 10 0.3 140 Example 81 1 5 1 10 0.3 140 Example 82 1 5 110 0.3 140 Example 83 1 5 1 10 0.3 140 Example 84 1 5 1 10 0.3 140Example 85 1 5 1 10 0.3 140

TABLE 37 Secondary layer Organic resin Rust inhibitor Solid lubricantCoating Baking Kind Blending Kind Blending Kind Blending thicknesstemperature Classification No. *9 quantity *11 *7 quantity *11 *10quantity *11 (μm) (° C.) Example 69 1 100 1 20 — — 1.0 140 Example 70 1100 1 20 — — 1.0 140 Example 71 1 100 1 20 — — 1.0 140 Example 72 1 1001 20 — — 1.0 140 Example 73 1 100 1 20 — — 1.0 140 Example 74 1 100 1 20— — 1.0 140 Example 75 1 100 1 20 — — 1.0 140 Example 76 1 100 1 20 — —1.0 140 Example 77 1 100 1 20 — — 1.0 140 Example 78 1 100 1 20 — — 1.0140 Example 79 1 100 1 20 — — 1.0 140 Example 80 2 100 1 20 — — 1.0 140Example 81 3 100 1 20 — — 1.0 140 Example 82 4 100 1 20 — — 1.0 140Example 83 5 100 1 20 — — 1.0 140 Example 84 6 100 1 20 — — 1.0 140Example 85 7 100 1 20 — — 1.0 140 Performance Corrosion resistanceCorrosion after Electrodeposited Classification No. resistance treatmentWeldability paint adhesion Example 69 ⊚ ◯+ ⊚ ⊚ Example 70 ⊚ ◯+ ⊚ ⊚Example 71 ⊚ ◯+ ⊚ ⊚ Example 72 ⊚ ◯+ ⊚ ⊚ Example 73 ⊚ ◯+ ⊚ ⊚ Example 74 ⊚◯+ ⊚ ⊚ Example 75 ⊚ ◯+ ⊚ ⊚ Example 76 ⊚ ◯+ ⊚ ⊚ Example 77 ⊚ ◯+ ⊚ ⊚Example 78 ⊚ ◯+ ⊚ ⊚ Example 79 ⊚ ◯+ ⊚ ⊚ Example 80 ⊚ ◯+ ⊚ ⊚ Example 81 ⊚⊚ ⊚ ⊚ Example 82 ◯+ ◯ ⊚ ⊚ Example 83 ◯+ ◯ ⊚ ⊚ Example 84 ◯+ ◯+ ⊚ ⊚Example 85 ⊚ ◯+ ⊚ ⊚

TABLE 38 Primary layer Water-soluble resin or water- Water dispersedSilane coupling Phosphoric acid or Plated dispersible resin polyurethaneresine agent hexafluorometal acid steel Blending Blending BlendingBlending Classification No. sheet *1 Kind *2 quantity *8 Kind *3quantity *8 Kind *4 quantity *8 Kind *5 quantity *8 Example 86 1 1 50 150 1 25 1 40 Example 87 1 1 50 1 50 1 25 1 40 Example 88 1 1 50 1 50 125 1 40 Example 89 1 1 50 1 50 1 25 1 40 Example 90 1 1 50 1 50 1 25 140 Comparative 91 1 1 50 1 50 1 25 1 40 example Comparative 92 1 1 50 150 1 25 1 40 example Comparative 93 1 1 50 1 50 1 25 1 40 exampleExample 94 1 1 50 1 50 1 25 1 40 Example 95 1 1 50 1 50 1 25 1 40Example 96 1 1 50 1 50 1 25 1 40 Comparative 97 1 1 50 1 50 1 25 1 40example Example 98 1 1 50 1 50 1 25 1 40 Comparative 99 1 1 50 1 50 1 251 40 example Comparative 100 1 1 50 1 10 1 25 1 40 example Comparative101 1 1 50 1 30 1 25 1 40 example Example 102 1 1 50 1 70 1 25 1 40Primary layer Water-soluble phosphate Rust inhibitor Coating BakingBlending Blending thickness temperature Classification No. Kind *6quantity *8 Kind *7 quantity *8 (μm) (° C.) Example 86 1 5 1 10 0.3 140Example 87 1 5 1 10 0.3 140 Example 88 1 5 1 10 0.3 140 Example 89 1 5 110 0.3 140 Example 90 1 5 1 10 0.3 140 Comparative 91 1 5 1 10 0.3 140example Comparative 92 1 5 1 10 0.3 140 example Comparative 93 1 5 1 100.3 140 example Example 94 1 5 1 10 0.3 140 Example 95 1 5 1 10 0.3 140Example 96 1 5 1 10 0.3 140 Comparative 97 1 5 1 10 0.3 140 exampleExample 98 1 5 1 10 0.3 140 Comparative 99 1 5 1 10 0.3 140 exampleComparative 100 1 5 1 10 0.3 140 example Comparative 101 1 5 1 10 0.3140 example Example 102 1 5 1 10 0.3 140

TABLE 39 Secondary layer Organic resin Rust inhibitor Solid lubricantCoating Baking Kind Blending Kind Blending Kind Blending thicknesstemperature Classification No. *9 quantity *11 *7 quantity *11 *10quantity *11 (μm) (° C.) Example 86 8 100 1 20 — — 1.0 140 Example 87 9100 1 20 — — 1.0 140 Example 88 10 100 1 20 — — 1.0 140 Example 89 11100 1 20 — — 1.0 140 Example 90 12 100 1 20 — — 1.0 140 Comparative 9113 100 1 20 — — 1.0 140 example Comparative 92 14 100 1 20 — — 1.0 140example Comparative 93 15 100 1 20 — — 1.0 140 example Example 94 16 1001 20 — — 1.0 140 Example 95 17 100 1 20 — — 1.0 140 Example 96 18 100 120 — — 1.0 140 Comparative 97 19 100 1 20 — — 1.0 140 example Example 9820 100 1 20 — — 1.0 140 Comparative 99 21 100 1 20 — — 1.0 140 exampleComparative 100 22 100 1 20 — — 1.0 140 example Comparative 101 23 100 120 — — 1.0 140 example Example 102 1 100 2 20 — — 1.0 140 PerformanceCorrosion resistance Corrosion after Electrodeposited Classification No.resistance treatment Weldability paint adhesion Example 86 ⊚ ◯+ ⊚ ⊚Example 87 ⊚ ⊚ ⊚ ⊚ Example 88 ⊚ ◯ ⊚ ⊚ Example 89 ⊚ ◯ ⊚ ⊚ Example 90 ⊚ ◯⊚ ⊚ Comparative 91 ◯ X ⊚ ⊚ example Comparative 92 ◯ X ⊚ ⊚ exampleComparative 93 ◯ X ⊚ ⊚ example Example 94 ⊚ ⊚ ⊚ ⊚ Example 95 ◯+ ◯+ ⊚ ⊚Example 96 ⊚ ◯+ ⊚ ⊚ Comparative 97 ◯ Δ ⊚ ⊚ example Example 98 ⊚ ◯+ ⊚ ⊚Comparative 99 Δ X ⊚ ⊚ example Comparative 100 Δ Δ ⊚ ⊚ exampleComparative 101 Δ Δ ⊚ ⊚ example Example 102 ◯+ ◯ ⊚ ⊚

TABLE 40 Primary layer Water-soluble Water dispersed Phosphoric acid orresin or water- polyurethane Silane coupling hexafluorometal Plateddispersible resin resine agent acid steel Blending Blending BlendingBlending Classification No. sheet *1 Kind *2 quantity *8 Kind *3quantity *8 Kind *4 quantity *8 Kind *5 quantity *8 Example 103 1 1 50 150 1 25 1 40 Example 104 1 1 50 1 50 1 25 1 40 Example 105 1 1 50 1 50 125 1 40 Example 106 1 1 50 1 50 1 25 1 40 Example 107 1 1 50 1 50 1 25 140 Example 108 1 1 50 1 50 1 25 1 40 Example 109 1 1 50 1 50 1 25 1 40Example 110 1 1 50 1 50 1 25 1 40 Example 111 1 1 50 1 50 1 25 1 40Example 112 1 1 50 1 50 1 25 1 40 Example 113 1 1 50 1 50 1 25 1 40Example 114 1 1 50 1 50 1 25 1 40 Example 115 1 1 50 1 50 1 25 1 40Primary layer Water-soluble phosphate Rust inhibitor Coating BakingBlending Blending thickness temperature Classification No. Kind *6quantity *8 Kind *7 quantity *8 (μm) (° C.) Example 103 1 5 1 10 0.3 140Example 104 1 5 1 10 0.3 140 Example 105 1 5 1 10 0.3 140 Example 106 15 1 10 0.3 140 Example 107 1 5 1 10 0.3 140 Example 108 1 5 1 10 0.3 140Example 109 1 5 1 10 0.3 140 Example 110 1 5 1 10 0.3 140 Example 111 15 1 10 0.3 140 Example 112 1 5 1 10 0.3 140 Example 113 1 5 1 10 0.3 140Example 114 1 5 1 10 0.3 140 Example 115 1 5 1 10 0.3 140

TABLE 41 Secondary layer Organic resin Rust inhibitor Solid lubricantCoating Blending Blending Blending thickness Classification No. Kind *9quantity *11 Kind *7 quantity *11 Kind *10 quantity *11 (μm) Example 1031 100 3 20 — — 1.0 Example 104 1 100 4 20 — — 1.0 Example 105 1 100 5 20— — 1.0 Example 106 1 100 6 20 — — 1.0 Example 107 1 100 7 20 — — 1.0Example 108 1 100 1 + 4 10 + 10 — — 1.0 Example 109 1 100 1 + 5 20 + 10— — 1.0 Example 110 1 100 1 + 6 20 + 10 — — 1.0 Example 111 1 100 1 +4 + 6 10 + 7 + 3 — — 1.0 Example 112 1 100 1 + 5 + 6 10 + 7 + 3 — — 1.0Example 113 1 100 4 + 5 + 6  9 + 8 + 3 — — 1.0 Example 114 1 100 — — — —1.0 Example 115 1 100 1  1 — — 1.0 Secondary Performance layer CorrosionBaking resistance temperature Corrosion after ElectrodepositedClassification No. (° C.) resistance treatment Weldability paintadhesion Example 103 140 ◯+ ◯ ⊚ ⊚ Example 104 140 ◯+ ◯ ⊚ ⊚ Example 105140 ◯+ ◯ ⊚ ⊚ Example 106 140 ◯ ◯− ⊚ ⊚ Example 107 140 ◯+ ◯ ⊚ ⊚ Example108 140 ⊚ ◯+ ⊚ ⊚ Example 109 140 ⊚ ◯+ ⊚ ⊚ Example 110 140 ⊚ ◯+ ⊚ ⊚Example 111 140 ⊚ ◯+ ⊚ ⊚ Example 112 140 ⊚ ◯+ ⊚ ⊚ Example 113 140 ⊚ ◯+ ⊚⊚ Example 114 140 ◯ ◯− ⊚ ⊚ Example 115 140 ◯ ◯− ⊚ ⊚

TABLE 42 Primary layer Water-soluble Water dispersed Phosphoric acid orresin or water- polyurethane Silane coupling hexafluorometal Plateddispersible resin resine agent acid steel Blending Blending BlendingBlending Classification No. sheet *1 Kind *2 quantity *8 Kind *3quantity *8 Kind *4 quantity *8 Kind *5 quantity *8 Example 116 1 1 50 150 1 25 1 40 Example 117 1 1 50 1 50 1 25 1 40 Example 118 1 1 50 1 50 125 1 40 Example 119 1 1 50 1 50 1 25 1 40 Example 120 1 1 50 1 50 1 25 140 Comparative 121 1 1 50 1 50 1 25 1 40 example Comparative 122 1 1 501 50 1 25 1 40 example Example 123 1 1 50 1 50 1 25 1 40 Example 124 1 150 1 50 1 25 1 40 Comparative 125 1 1 50 1 50 1 25 1 40 exampleComparative 126 1 1 50 1 50 1 25 1 40 example Example 127 1 1 50 1 50 125 1 40 Example 128 1 1 50 1 50 1 25 1 40 Example 129 1 1 50 1 50 1 25 140 Primary layer Water-soluble phosphate Rust inhibitor Coating BakingBlending Blending thickness temperature Classification No. Kind *6quantity *8 Kind *7 quantity *8 (μm) (° C.) Example 116 1 5 1 10 0.3 140Example 117 1 5 1 10 0.3 140 Example 118 1 5 1 10 0.3 140 Example 119 15 1 10 0.3 140 Example 120 1 5 1 10 0.3 140 Comparative 121 1 5 1 10 0.3140 example Comparative 122 1 5 1 10 0.3 140 example Example 123 1 5 110 0.3 140 Example 124 1 5 1 10 0.3 140 Comparative 125 1 5 1 10 0.3 140example Comparative 126 1 5 1 10 0.3 140 example Example 127 1 5 1 100.3 140 Example 128 1 5 1 10 0.3 140 Example 129 1 5 — — 0.3 140

TABLE 43 Secondary layer Organic resin Rust inhibitor Solid lubricantCoating Blending Blending Blending thickness Classification No. Kind *9quantity *11 Kind *7 quantity *11 Kind *10 quantity *11 (μm) Example 1161 100 1 50 — — 1.0 Example 117 1 100 1 30 — — 1.0 Example 118 1 100 1 201 5 1.0 Example 119 1 100 1 20 2 5 1.0 Example 120 1 100 1 20 3 5 1.0Comparative 121 — — — — — — — example Comparative 122 1 100 1 20 1 5 1.0example Example 123 1 100 1 20 1 5 1.0 Example 124 1 100 1 20 1 5 1.0Comparative 125 1 100 1 20 1 5 1.0 example Comparative 126 1   100 ※ 120 1 5 1.0 example Example 127 1 100 1 20 2 5 1.0 Example 128 1 100 1 202 5 1.0 Example 129 1 100 1 20 2 5 1.0 Secondary Performance layerCorrosion Baking resistance temperature Corrosion after ElectrodepositedClassification No. (° C.) resistance treatment Weldability paintadhesion Example 116 140 ⊚ ◯ ◯ ⊚ Example 117 140 ⊚ ◯+ ◯ ⊚ Example 118140 ⊚ ⊚ ⊚ ⊚ Example 119 140 ⊚ ⊚ ⊚ ⊚ Example 120 140 ⊚ ⊚ ⊚ ⊚ Comparative121 — X X ⊚ ⊚ example Comparative 122 140 Δ Δ ◯ ⊚ example Example 123140 ◯ ◯ ◯ ⊚ Example 124 140 ⊚ ⊚ ◯ ◯ Comparative 125 140 ⊚ ◯+ X X exampleComparative 126 140 ⊚ X ◯ ◯ example Example 127 110 ⊚ ◯+ ⊚ ⊚ Example 128200 ◯ ◯ ⊚ ⊚ Example 129 140 ⊚ ⊚ ⊚ ⊚ ※ As the conductive agent, 80 partsby mass of iron phosphide is added to 100 parts by mass of the solidmatter in the resin composition.

1. A surface-treated steel sheet with excellent corrosion resistancecomprising: a zinc-based plated steel sheet or an aluminum-based platedsteel sheet; a surface-treatment coating disposed on a surface of theplated steel sheet having a coating thickness ranging from 0.01 to 1 μm,and being formed by applying and drying a surface-treatment coatingcomposition which contains ingredients (a) through (c) described below;and a top coating having a coating thickness ranging from 0.3 to 2 μm,and being formed by applying and drying a coating composition for topcoating, containing an (E) high molecular weight epoxy group-containingresin having a number average molecular weight ranging from 6000 to20000 on the surface-treatment coating: (a) a water-epoxy resindispersion which is prepared by dispersing in water a resin obtained bya reaction of: an (A) polyalkyleneglycol-modified epoxy resin derivedfrom a reaction of polyalkyleneglycol having a number average molecularweight ranging from 400 to 20000, a bisphenol type epoxy resin, anactive hydrogen-containing compound for blocking an isocyanate group,and a polyisocyanate compound; a (B) epoxy group-containing resin otherthan the (A) polyalkyleneglycol-modified epoxy resin; and an activehydrogen-containing compound which reacts with an epoxy group in the (A)polyalkyleneglycol-modified epoxy resin and the (B) epoxygroup-containing resin, a part or all of the active hydrogen-containingcompound being a (C) hydrazine derivative having active hydrogen; (b) asilane coupling agent in an amount ranging from 1 to 300 parts by massof solid matter therein to 100 parts by mass of the resin solid matterin the water-epoxy resin dispersion; and (c) phosphoric acid and/or ahexafluorometal acid in an amount ranging from 0.1 to 80 parts by massof solid matter therein to 100 parts by mass of the resin solid matterin the water-epoxy resin dispersion.
 2. The surface-treated steel sheetaccording to claim 1, wherein the (C) hydrazine derivative containingactive hydrogen is at least one compound selected from the groupconsisting of a pyrazole compound and a triazole compound, whichcompound has a ring structure of five-membered ring or six-memberedring, and has nitrogen atom in the ring structure.
 3. Thesurface-treated steel sheet according to claim 2, wherein thesurface-treatment coating composition further contains a water-solublephosphate in an amount ranging from 0.1 to 60 parts by mass of solidmatter therein to 100 parts by mass of the resin solid matter in thewater-epoxy resin dispersion of the ingredient (a).
 4. Thesurface-treated steel sheet according to claim 1, wherein thesurface-treatment coating composition further contains a water-solublephosphate in an amount ranging from 0.1 to 60 parts by mass of solidmatter therein to 100 parts by mass of the resin solid matter in thewater-epoxy resin dispersion of the ingredient (a).
 5. Thesurface-treated steel sheet according to claim 1, wherein thesurface-treatment coating composition further contains at least onenon-chromium based rust inhibitor in an amount ranging from 0.1 to 50parts by mass of solid matter therein to 100 parts by mass of the resinsolid matter in the water-epoxy resin dispersion of the ingredient (a).6. The surface-treated steel sheet according to claim 5, wherein the atleast one non-chromium based rust inhibitor is selected from the groupconsisting of (e1) silicon oxide, (e2) calcium and/or a calciumcompound, (e3) a slightly-soluble phosphoric acid compound, (e4) amolybdic acid compound, (e5) a vanadium compound, (e6) an organiccompound containing a S atom, being one or more compounds selected fromthe group consisting of triazole, thiol, thiaziazole, thiazole andthiuram and (e7) an organic compound containing a N atom, being one ormore compounds selected from the group consisting of a hydrazidecompound, a pyrazole compound, a triazole compound, a tetrazolecompound, a thiaziazole compound and a pyridazine compound.
 7. Thesurface-treated steel sheet according to claim 1, wherein the coatingcomposition for top coating further contains at least one non-chromiumbased rust inhibitor in an amount ranging from 0.1 to 50 parts by massof solid matter therein to 100 parts by mass of the resin solid matterin the coating composition.
 8. The surface-treated steel sheet accordingto claim 7, wherein the at least one non-chromium based rust inhibitoris selected from the group consisting of (e1) silicon oxide, (e2)calcium and/or a calcium compound, (e3) a slightly-soluble phosphoricacid compound, (e4) a molybdic acid compound, (e5) a vanadium compound,(e6) an organic compound containing a S atom, being one or morecompounds selected from the group consisting of triazole, thiol,thiaziazole, thiazole and thiuram and (e7) an organic compoundcontaining a N atom, being one or more compounds selected from the groupconsisting of a hydrazide compound, a pyrazole compound, a triazolecompound, a tetrazole compound, a thiaziazole compound and a pyridazinecompound.
 9. The surface-treated steel sheet according to claim 1,wherein the coating composition for top coating further contains acuring agent having a group which crosslinks with a hydroxyl group, inan amount ranging from 1 to 50 parts by mass of solid matter therein to100 parts by mass of the solid matter in the (E) high molecular weightepoxy group-containing resin.
 10. The surface-treated steel sheetaccording to claim 9, wherein the curing agent having a groupcrosslinking with a hydroxyl group is an (F) amino resin which has oneor more imino groups as an average within a single molecule thereof. 11.The surface-treated steel sheet according to claim 9, wherein the curingagent having a group crosslinking with a hydroxyl group is a (G)polyisocyanate compound which has four or more isocyanate groups as anaverage within a single molecule thereof.
 12. The surface-treated steelsheet according to claim 11, wherein the (G) polyisocyanate compound hasat least some of the isocyanate groups in the polyisocyanate compoundwhich are blocked by a blocking agent.
 13. The surface-treated steelsheet according to claim 1, wherein the (E) high molecular weight epoxygroup-containing resin in the coating composition for top coating is amodified epoxy group-containing resin which is modified by an (H) activehydrogen-containing compound which reacts with an epoxy group, a part orall of the active hydrogen-containing compound is an (I) hydrazinederivative having active hydrogen.
 14. The surface-treated steel sheetaccording to claim 13, wherein the active hydrogen-containing compoundwhich reacts with an epoxy group is selected from the group consistingof carbohydrazide, hydrazide propionate, hydrazide salicylate,dihydrazide adipate, dihydrazide sebacylate, dihydrazide dodecanate,dihydrazide isophthalate, thiocarbohydrazide, 4,4′-oxybisbenzenesulfonylhydrazide, benzophenone hydrazone and aminopolyacrylamide.
 15. Thesurface-treated steel sheet according to claim 1, wherein the coatingcomposition for top coating further contains a solid lubricant in anamount ranging from 1 to 30 parts by mass of solid matter therein to 100parts by mass of the resin solid matter in the coating composition. 16.The surface-treated steel sheet according to claim 1, wherein theactive-hydrogen containing compound for blocking an isocyanate group isselected from the group consisting of a monohydric alcohol, a monohydriccarboxylic acid, a monohydric thiol, a secondary amine and an oximecompound.
 17. The surface-treated steel sheet according to claim 1,wherein the active-hydrogen containing compound for blocking anisocyanate group is selected from the group consisting of methanol,ethanol, diethylenglycol monobutyl ether, acetic acid, propyonic acid,ethylmercaptan, diethylamine, methylethylketoxime, phenol andnonylphenol.
 18. A method for manufacturing surface-treated steel sheetwith excellent corrosion resistance comprising the steps of: (i)applying a surface-treatment coating composition which contains (a) awater-epoxy resin dispersion, (b) a silane coupling agent and (c)phosphoric acid and/or a hexafluorometal acid onto a surface of azinc-based plated steel sheet or an aluminum-based plated steel sheet,and then drying the applied surface-treatment coating composition at anultimate sheet temperature ranging from 30° C. to 150° C., thus forminga surface-treatment coating having a coating thickness ranging from 0.01to 1 μm; and (ii) forming a top coating having a coating thicknessranging from 0.3 to 2 μm on the surface-treatment coating by applying acoating composition for top coating containing an (E) high molecularweight epoxy group-containing resin having a number average molecularweight ranging from 6000 to 20000, and then by drying the appliedcoating composition for top coating at an ultimate sheet temperatureranging from 30° C. to 150° C.; said water-epoxy resin dispersion (a) isprepared by dispersing in water a resin obtained by a reaction of: an(A) polyalkyleneglycol-modified epoxy resin derived from a reaction ofpolyalkyleneglycol having a number average molecular weight ranging from400 to 20000, a bisphenol type epoxy resin, an activehydrogen-containing compound for blocking an isocyanate group, and apolyisocyanate compound; a (B) epoxy group-containing resin other thanthe (A) polyalkyleneglycol-modified epoxy resin; and an activehydrogen-containing compound which reacts with an epoxy group in the (A)polyalkyleneglycol-modified epoxy resin and the (B) epoxygroup-containing resin, a part or all of the active hydrogen-containingcompound being a (C) hydrazine derivative having active hydrogen; saidsilane coupling agent being in an amount ranging from 1 to 300 parts bymass of solid matter therein to 100 parts by mass of the resin solidmatter in the water-epoxy resin dispersion; and said phosphoric acidand/or a hexafluorometal acid (c) being in an amount ranging from 0.1 to80 parts by mass of solid matter thereof to 100 parts by mass of theresin solid matter in the water-epoxy resin dispersion.